In France, the elections read like a 3-way Sanders - Clinton - Trump fight. The difference with the U.S. is that the voters at large get to pick the finalists, not the party voters.

It could make sense for the anti-Merkel vote to move left. Since no major party would align with the AfD, Germany needs the Social Democrats to out-poll the Christian Democrats, at least to the extent of being the dominant party of a "grand coalition" of SD-CD.