Rue89 has a good piece on the effect of polling on primary voters. The argument is simple: had it not been for polls showing that Ségolène Royal was the best-placed Socialist candidate to beat Sarkozy in 2007, she wouldn't have won the primary, and look how that worked out.
Indeed, as the article points out, when ideological differences between candidates are small, primary voters tend to be unduly influenced by horse-race polling, which is notoriously inaccurate. After all, none of the contenders has really been tested against the true opposition, voters are notoriously fickle, and much can happen in the many months between now and the presidential election.
At the moment, François Hollande appears to enjoy a not insignificant lead both in polling against Sarkozy and in comparison with other Socialist candidates. This probably reflects his assiduous efforts: by campaigning constantly, he has kept his name in the news and not just at the national level. One can't accuse him of not working hard for the nomination. Are there other factors? Does he seem a more likely "incarnation" of the presidency than his rivals? Are primary voters, disappointed with their choice of a woman last time around, looking for a man this time? Has Aubry failed to convince or connect?
I really don't know. The polling methodologies in France are too various and haphazard to have much confidence in their ability to pick winners or even to identify likely primary voters (France needs a poll critic like Nate Silver in the U.S., who can separate the wheat from the chaff). I frankly don't sense much enthusiasm among my Socialist friends for either Aubry or Hollande. Faute de mieux, either one will do. The primary campaign hasn't stirred much of a debate yet about anything important, and both leading candidates are cautious in the extreme, as well as seasoned enough to avoid major gaffes. So we just have to wait to see who staggers across the finish line first. As for Montebourg, Valls, Royal, and the other guy (Baylet, qui ça?), yeah, sure, anything could happen, but ...