What would national politics in Washington look like with a wholly Republican Congress and a Democratic White House? That could be the situation after the coming midterms, and if it is, the past can give us at least a hint of what it might mean.

In a reminder of how delightfully quaint American politics once were, observers just shy of a century ago believed that President Woodrow Wilson lost control of Congress in 1918 because he made a mild campaign pitch for Democratic Party congressional candidates. In late October, Wilson released a statement asking voters to re-elect the Democratic House and Senate majorities. “In ordinary times I would not feel at liberty to make such an appeal to you. But these are not ordinary times”, Wilson wrote, alluding to the World War still raging across the Atlantic.

The Democrats wound up losing the House and the Senate. Two of Wilson’s Cabinet officials “claimed afterward that [the statement] inflamed partisan passions and that the Democrats would have won if Wilson had just kept his mouth shut.” So writes John Milton Cooper, Jr. in his recent Woodrow Wilson: A Biography, adding that “contemporary charges and wise hindsight about the appeal were overworked” and that “high prices, wartime shortages, and myriad inconveniences” were a more likely cause for the Democrats’ midterm setback.

While partisan statements, even weak ones, were frowned upon a century ago, voters were awfully partisan themselves in that era. For instance, two years later in the 1920 presidential election, in only 11 of 344 congressional districts did voters support a different party in the presidential race and in their local House race.¹ And they rarely saddled Presidents with what they had just dumped on Wilson: a Congress completely controlled by the party that did not hold the White House.

The post-Civil War era in American history spans 149 years. In that century and a half, a President has faced a Congress entirely controlled by the opposite party only about a quarter of the time: 36 years out of 149. But for the first half of that timeframe—the period between the end of the Civil War and the start of World War II—completely opposite control of the two ends of Pennsylvania Avenue was exceedingly rare: just six out of the 75 years from 1865 to 1940. (One such time was 1919–21, Wilson’s final two years. This does not include, however, the four years of Andrew Johnson’s presidency, even though one could argue that the former Democrat-turned-Union Party running mate of Republican President Abraham Lincoln faced unified opposition control of Congress for his entire presidency.)

After World War II, however, truly divided government occurred more frequently. There’s an easy structural explanation for this: From 1945 to 1995, Democrats controlled the House for 46 of a possible fifty years, and the Senate for forty of fifty years. In that same period, Republicans had a slight edge in the White House, controlling it for 28 of fifty years. This partisan split between presidential and congressional results can largely be explained by the South, which remained solid for congressional Democrats throughout this era while trending Republican at the presidential level throughout the postwar period. (The region is now heavily Republican at the congressional level, too.)

The congressional-presidential disconnect in the Cold War era also explains why the only three post-Civil War Presidents to face a Congress entirely controlled by the opposition for the entirety of their terms—Richard Nixon, Gerald Ford, and George H.W. Bush—were all Republicans. (Four Democratic Presidents faced a wholly Republican Congress for part of their terms: Grover Cleveland, Wilson, Harry Truman, and Bill Clinton.) Perhaps it’s not surprising that all three of these Republican Presidents are now considered less conservative on domestic policy than their current contemporaries, given that they never had the opportunity to work with a cooperative, like-minded conservative Congress. That said, Ronald Reagan retains his iconic status with modern Republicans, even though the GOP never controlled the House in his time in office. (It did control the Senate for his first six years in office.)

Like Reagan and George W. Bush—recent two-term Presidents who suffered through poor election results in the second midterm over which they presided—President Obama might be doomed to a Congress that is completely, instead of just partially, opposed to him and his policies for his final two years. One half of the equation is essentially set: The House is almost certain to remain in Republican hands for the third straight Congress. Since the Civil War, the party that controls the White House has never netted 17 seats, the number Democrats need to take the House, in a midterm election. Furthermore, the President’s party has lost ground in the House in 35 of 38 midterms conducted in that time frame.

There are decent odds—probably better than 50-50, but not dramatically so—that the Republicans will take control of the Senate, too. They can do so simply by keeping all of their existing seats and adding six to their current 45, all of which could come from states where President Obama received less than 42 percent of the vote in 2012. Let’s say it happens. What then?

From a policy standpoint, it’s hard to say if Washington would be dramatically more gridlocked and unproductive with a unified GOP Congress opposing President Obama, if only because Federal policymaking has been at a standstill ever since the GOP took the House in 2010. Comprehensive immigration reform would remain highly unlikely, even if elites on the Republican side would like to get the issue off the table in advance of the 2016 presidential election (and they would, but they can’t). Rank-and-file members of the House Republican caucus are not sold on the idea as a policy matter, a view strongly reinforced by party activists. A Republican Senate would add yet another roadblock to action on this issue.

With Obama’s veto pen in place, and the impossibility of Republicans winning a veto-proof majority in the House or the Senate, the GOP likely could only nibble at the edges of already-enacted policy, like the Affordable Care Act. Republicans likely would attempt to repeal “Obamacare” if only to force an Obama veto. National Journal’s Sam Baker recently suggested that actual changes to the law would likely target provisions that generate revenue to pay for the act, like the law’s tax on medical devices, rather than provisions that voters like, such as restoring insurers’ ability to refuse coverage to people with pre-existing conditions. As always, it’s easier for Congress to give than to take.

It’s easy, therefore, to imagine that 2015 and 2016 will be defined more by posturing than by policymaking. Republicans will have every incentive to make Obama look bad ahead of the 2016 election, because his approval rating, if low enough, might be enough to prevent a Democrat—even Hillary Clinton—from winning a third consecutive Democratic term in the White House. One way to harm Obama is to continue investigating various Administration scandals, and they would have greater ability to do so with control of the Senate.

Brendan Nyhan, a Dartmouth University professor and expert on presidential scandals, has not found much relationship between divided government or unified opposition control of Congress and an increase in presidential scandals in his research, which goes back to the late 1970s. Political scientists David C.W. Parker of Montana State University and Matthew Dull of Virginia Tech University found in a 2009 study that “divided government generates more and more-intensive congressional investigations, but this relationship is contingent on partisan and temporal factors.” It’s easy to imagine Republican investigations of the Obama Administration generating more attention if the Senate got into the act: One tangible difference could be that a Republican Senate would set up its own committee to investigate Benghazi, like House Republicans have already done.

Of course, Republicans might push their various scandal investigations so far that they backfire and end up benefiting Democrats in the public eye. President Clinton was probably helped politically by Republicans’ ravenous pursuit of him in 1998 over the Monica Lewinsky affair: The Democrats actually added House seats in November, a midterm rarity for the President’s party. Impeachment could be repeated—even now, the Republican House majority could hypothetically impeach the President at any time—but the hopelessness (a two-thirds majority of the Senate is required to convict) and divisiveness of such a move would almost certainly be a massive political overreach.

Perhaps more interesting than the pursuit of scandal would be a possible, and an historic, showdown over the Supreme Court. Assuming Republicans could keep their caucus together—a big “if” that greatly depends on the size of a new majority—a Republican-led Senate could potentially reject any and all Obama nominees for Administration positions and judicial appointments. That includes anyone Obama would nominate for a hypothetical Supreme Court vacancy. Given the immense value to both parties of lifetime Supreme Court appointments, it’s worth considering the potential for a truly historic and divisive showdown between Obama and the Senate over a Supreme Court nomination.

It’s not uncommon for presidential nominations to the Supreme Court to fail for one reason or another: Since 1789, Presidents have submitted 160 Supreme Court nominations to the Senate, including those for Chief Justice (who sometimes is already a member of the court). Of those, 124 were confirmed (seven declined to serve). But even though Supreme Court nominees sometimes withdraw or are rejected, the President, at the time the vacancy occurs or is announced, almost always eventually fills it with a nominee of his choosing.

Almost always: Only twice in the post-Civil War era has a President presented with a Supreme Court vacancy failed to fill it before leaving office.² The most recent instance was nearly half a century ago, in 1968, when Chief Justice of the United States Earl Warren announced his intention to retire upon the confirmation of his successor. Outgoing President Lyndon B. Johnson nominated Justice Abe Fortas, his longtime friend and confidante whom he had appointed to the court in 1965, to replace Warren as Chief Justice. The Democratic-controlled Senate refused to confirm him, though, and Johnson withdrew his nomination in October 1968, along with the nomination of Homer Thornberry, a Federal appellate judge Johnson had nominated to replace Fortas. Warren stayed on as Chief Justice, and it fell to Johnson’s successor, President Richard Nixon, to fill the seat. Nixon picked Warren Burger as Chief Justice.

Prior to that, one has to go back to 1881 to find a court vacancy that was filled not by the sitting President but by his successor. President Rutherford B. Hayes made the controversial nomination of Stanley Matthews in 1881. The nomination came near the end of Hayes’s term, so the Senate did not act. New President James A. Garfield renominated Matthews, and he passed through the Senate by a slim 24–23 vote.

Despite the lack of any recent precedent for such a power play, nothing but public pressure and historical norms would stop the GOP from running out the clock until the end of Obama’s term on a Supreme Court nomination, potentially preserving the court opening for a Republican President, should one be elected in 2016. This would be just the latest escalation in a procedural arms race in the Senate: Democrats responded to Republican obstruction of President Obama’s appointments by changing Senate filibuster rules to push through judicial and other nominees (though, notably, these rule changes preserved a filibuster for Supreme Court nominations). Regardless, the Republicans can simply up the ante if they take control.

However, it’s an open question whether the GOP could hold its Senate caucus together for such a bracing battle: Less conservative members of the caucus, like Senators Susan Collins of Maine or Lisa Murkowski of Alaska, might not go along, and several potentially endangered Republican Senators in generally blue states—Ron Johnson of Wisconsin, Mark Kirk of Illinois, and Pat Toomey of Pennsylvania—might not invite the political pressure as they attempt to win second terms in 2016. But in an era of seemingly unceasing conflict between President Obama and the Republicans, battles that seem farfetched could become very likely.

One of the Senate’s fundamental and historic duties is to be consulted on matters of war and peace. The great consequence of Wilson’s Democrats losing the Senate in 1918 was that the President’s Republican nemesis, Senator Henry Cabot Lodge of Massachusetts, became the Chairman of the Foreign Relations Committee. Six days after the midterm election, World War I ended, and Lodge defeated Wilson in the later battle to ratify the Treaty of Versailles. “Like most midterm contests, this one turned chiefly on domestic and local issues rather than foreign affairs, even though a war was raging”, writes Cooper of the election that empowered Lodge. But arguably the greatest effect of the midterm was on foreign affairs.

The past few months have been dominated by international strife: crisis in Iraq and the Middle East, as well as in Ukraine. International affairs almost certainly will not be driving the decisions of voters this fall, but the choices they make could greatly affect how the United States deals with that strife all the same.