The more one sees of the Republican field, the more it seems clear that President Obama’s biggest problems do not come from his domestic opponents. The more voters, even Republican voters, learn about the candidates jostling for the party’s nod, the less they like them. The more the President’s opponents campaign, the stronger the White House becomes.The primaries and caucuses that really worry the White House are happening in Europe. Elections in Greece and caucuses in Brussels at this point will do more to determine the President’s fate in 2012 than anything that happens in Iowa or New Hampshire.The reason isn’t that Americans have suddenly developed a deep interest in European politics. The reason is that in the absence of a strong and compelling opponent in 2012, President Obama’s chances of re-election start to look much better with even modest improvements in the US economy — and those improvements are starting to appear. GDP growth is up, the stock market had a huge rally in October, and some hard hit midwestern states like Michigan are showing some bounce. It’s beginning to look that if the domestic economy is left to its own devices, the President will be able to argue that the economy is on the mend. He may not be riding a boom, but with a weak opponent modest growth could be enough.This of course is where the Europeans come in. As the week’s upheaval in Europe amply demonstrates, Europe is so poorly organized, so weakly led and in such deep trouble that as so often in the twentieth century, European failures threaten the whole world with chaos and catastrophe. Like two rock climbers on a cliff, the US and Europe are tethered together. The US slipped and almost fell in 2008 and 2009; we have now recovered our footing, but our European partner is in danger of falling. If Europe goes down, we are likely to follow.If the US economy crashes again, President Obama can be easily beaten by even a weak and unloved opponent. That means that President Obama’s grip on the White House may largely be up to Merkel and Sarkozy; if they can keep Europe afloat, they will save President Obama as well as the Greeks.Gideon Rachman over at the Financial Times has an important column that examines the linkage between President Obama and the EU in real depth; Rachman makes the point that new economic problems in the US caused by European failures won’t just hurt Obama by weakening the economy. They will also make it easier for Republicans to frame the election as a choice between Obama’s adherence to a “failed European model” and the red blooded American capitalism that Republicans love. Read the whole thing.Arguably Herbert Hoover’s re-election hopes were destroyed when a modestly improving US economy in 1931 was knocked on the head by the consequences of a European banking crisis; President Obama is vulnerable to the same fate, and as in President Hoover’s case, except for waiting and hoping, there may not be much he can do.