For Jean-Luc Mélenchon, the Harris polls that have everyone talking are worthless. He explains his reasoning at length here. If you pare away the bluster, he even makes a few valid points. But he neglects to say that he has an interest in discrediting the poll, because one effect of a strong FN is to persuade defectors from the PS, tempted to cast a first-round vote for the PG as a protest against the fecklessness of the PS, that they had better return to the fold lest the Left find itself left out of the second round as in 2002. Indeed, one of the complexities of a two-round system for pollsters is that each poll multiplies the opportunities for voters to register "expressive" rather than "instrumental" preferences. That is, it's perfectly possible to intend to vote PS but to say that you're going to vote PG or NPA in order to "send a message" of discontentment to the PS. And the greater the fragmentation of the sample group, the larger the margin of error.
I'd like to comment on one other point that Mélenchon mentions in his blog: Radio J has canceled an invitation to Marine Le Pen at the behest of the CRIF. This is a very bad business. Like it or not, the Front National is now a mainstream political party. Marine Le Pen is not her father and cannot be taxed with the sins of her father. One may suspect all the continuities one wants, but one also has to acknowledge the change in the surface. Jean-Marie mocked les fours crématoires; Marine denounces rather than denies the Holocaust. She has to be confronted head on and debated straight up, not excluded, and certainly not excluded from the airwaves by a Jewish organization. For a religious group to exclude a presidential candidate from the airwaves on the grounds that she is her father's daughter and therefore prima facie guilty of an anti-Semitism she explicitly denies simply cannot be tolerated. Free speech is free speech, and Marine Le Pen has to be faced squarely. On this point, I agree entirely with Mélenchon: the president of the CRIF is "juste quelqu’un qui veut exercer un pouvoir normatif communautaire sur la liberté de parole des autres." This is unacceptable.