Even if the Communists and Trotskyites do not deliberately urge their voters to back Le Pen, many of them will certainly do so anyway.
Only in France! Not only do the French have Trotskyites, something I thought had vanished from the face of the earth in the 1940's (or earlier), but they are upset that Le Pen could win. If he does win, it will be interesting to see what the European Union does. If you remember when Austria elected some folks who were 'nationalists,' the European Union had fits of a Nazi resurgence in Austria and threatened to kick Austria out of the union if they didn't trottle this political party.
If Le Pen wins, I would Expect the European Union to do its thing again and I would also expect that the French (always nationalistic) would pull out from the union and tell them to leave Strassburg. Could be an interesting showdown.
Maybe not his followers but Trotsky certainly vanished at that time.