Your challenge, should you choose to accept it, is to make National Front to win French legislative elections in 2012. POD shouldn't be any earlier than 2005 and the president should be preferably from another party.
That's pretty much impossible considering the history of the party. It has been percieved as a neo-fascist party by the media and most of the population for ages, basically until Marine le Pen was elected president, purged the more extreme elements and sued anyone that accused her to be a "nazi".
With a POD so early, it would require that:
-many more people in the media support them (most journalists are left-side so it'd be difficult)
-The other two big parties, PS (social-democrat) and UMP (center-right) somehow collapse
-Worse economic crisis, more immigration, criminality, etc. basically what could push people to vote for a nationalist party
An alliance with the UMP in the legislative elections is more likely. The top leadership of the UMP is against that, but if their results are worse in the previous elections they might change their minds.