Mr. Macron is a big target for the populists, because he has gone out of his way to deride them and set himself up as the defender of Europe and increased federalism against those who want to disrupt it.
Italy is also important. Mr. Salvini will do well, but how well? If his League significantly outscores his coalition partner, the populist left-wing Five Star Movement, he may decide to break the coalition and call new elections to try to become prime minister.
Polls indicate that Italians may be getting tired of Mr. Salvini, but how tired?
In Poland, too, these elections will be seen as a marker on the performance of Law and Justice, which is sharply criticized by Brussels for its Hungary-like efforts to distort and control the judicial system.
Law and Justice, which strongly favors European membership but wants less interference from Brussels, faces a collection of opposition parties calling itself the European Coalition. Poland has national elections this autumn, probably in October, and this vote will be considered a guide to that more important one.
The German vote will be seen as a judgment on the floundering center-left Social Democratic Party, the far-right Alternative for Germany and on the new leader of the Christian Democrats, Annegret Kramp-Karrenbauer, who hopes to succeed Chancellor Angela Merkel.
Austria will also be interesting, since this election will be the first chance for voters to judge the breakup of the country’s governing coalition of the center right and far right, after the resignation of far-right Vice Chancellor Heinz-Christian Strache and his colleagues over a video that raised questions over Russian influence on their party. Will Chancellor Sebastian Kurz and his People’s Party be rewarded or punished?
Then there is Britain, which voted to leave the European Union three years ago, but finds itself voting for a European Parliament anyway, since it has not managed to agree on how to make Brexit work.