The latest CSA poll (dated March 22) shows Sarkozy at 30%, 2 points ahead of Hollande. Le Pen at 13.5 slightly leads Bayrou and Mélenchon, tied at 13. Mélenchon 13%! And look at the dynamic. He's the one with the momentum, while Le Pen is down sharply and Bayrou has flatlined.
I don't know whether this polling was done after the slaughter in Toulouse or not. And I hesitate to overinterpret the results of any poll. But I think that this one confirms a trend that has been noticeable for a while now. Hollande's campaign is not cutting it. His strategy--to lie low and say as little as possible, counting on anti-Sarkozy sentiment to put him over--wasn't working before Toulouse and is even less likely to work now. Meanwhile, voters on the right who had deserted Sarkozy have been reminded that while Marine Le Pen's rhetoric may be music to their ears, there are reasons to want to hold actual power, and Sarkozy is the only candidate on the right with a chance of doing that. So if their reaction to Toulouse is one of anger and wanting to strike back (at somebody, anybody), as was the case in the US after 9/11, then they had better vote for Sarkozy. So they are deserting Le Pen and falling back into line.
Meanwhile, on the left, the Mélenchon phenomenon is confirmed. The coverage of the Bastille event gave him a big boost, but even more than that, Hollande's failure to propose, oppose, or impose while the frontrunner has led growing numbers of voters on the left to think that they must register a protest--now or never--in order to light a fire under their feckless candidate. Of course the second-round remains crucial, but the second-round dynamic may have shifted as well since Toulouse. Some of Bayrou's voters have no doubt swung back toward the right, worrying that Hollande is too weak to deal with either domestic terrorism or a reinvigorated extreme left, trade unions, etc. Like it or not, the events in Toulouse work in favor of an executive capable of projecting firmness and strength--and this is not Hollande's long suit.