Opinion polls suggest they could win up to 180 seats.

The races are seen as the best barometer of just how angry and alienated Europe really is — and just how broadly populists of various stripes can break through after years of gaining political strength.

As the populists are playing to anger and nationalism, mainstream leaders are trying to sell their apathetic voters on maintaining the course.

Reality: Populists are not expected to win the biggest number of the Parliament’s 751 seats, let alone a majority. Still, analysts predict a major electoral breakthrough that is certain to disrupt European politics.

A big question is whether the varied populists, assuming they win a sizable number of seats, can coalesce into a powerful coalition.

Context: The recent scandal in Austria, which forced the resignation of the far-right Freedom Party vice chancellor and the collapse of the government on Saturday, may also damage the populist surge, reminding voters of how close many of these parties are to Russia.