Here is what i meant about the extreme right growth.
Nicolas Sarkozy during his whole term has been playing communities against each other and designating scapegoats for each issue. Of course, the #1 scapegoat is the immigrants. Of course, this is the usual themes defended by the extreme right, taken over by the traditional right.
As WWII is still in the mid of the older generations who had a chance to learn history, there is a general poison that the thesis of the extreme right are not acceptable. This was especially true with Jean Marie Le Pen, who had been directly involved in killing people and in torturing in the war in ALgeria, and surrounded by collaborationists from WWII. His daughter is much smarter. She tried to make the extreme right more presentable, and to get away rom the negative image of her father.
Nicolas Sarkozy, by using the anti immigrants, racist, anti EU, etc.... arguments from the extreme right made these arguments more acceptable. In the past National Front voters used to hide, not to declare they voted for the extreme right. Now, making these ideas more acceptable, allows people to revendicate they voted for the extreme right,a nd more to follow suit.
I hope you will understand my point, even if you may be lacking some background on French politics for the art few decades. If not, don't hesitate to ask more questions.