thanks for your comment mnemos. I  was going to add that a range of different interpretations to the poll numbers are certainly possible, and that a week in politics is a lifetime. But my word limit was reached. So yes your comments are valid. That having been said and admitted,a few comments 

While its true that polls from a year or so ago don't carry the weight of more current polls, polling over time can show a trend, and Le Pens opponents no doubt would say Le Pens downward trend is due to voters paying more attention and continued and more incessant critiques of Le Pen showing impact.

Second, while left right are weaker than in the past,  its  valid to point out that much of  her working class support is already reflected in Le Pen support which has been there for her in the rust belt of  france, since local and other  election campaigns  over the past year or so, as Le Pen contests district and other elections in the old industrial former leftwing strongholds of NE France.