ATHENS — This time, there are no predictions of doom, no anguished fretting out of Washington or Berlin that Greek national elections could unravel the European economic order. That was the mood in 2012, when the fate of the euro seemed to hang on the whims of an angry Greek electorate that, in the end, voted to stay the course in the euro zone.

The dynamics seem reversed as Greeks return to the polls this weekend for European parliamentary elections. The balloting, from Thursday through Sunday, is supposed to represent another developmental step in the broader European political project, but an expected protest vote across Europe means that the impact may be greater on national politics.

In Greece, the vote has become a de facto referendum on the governing coalition and a test of whether ordinary citizens believe the government’s assertion that the country is finally on the upswing. Polls are showing the left-wing opposition party, Syriza, with a slight advantage over New Democracy, the center-right party that leads the government.

“If the margin is large, on the order of 5 percent or more, this could be destabilizing,” said Harry Papasotiriou, a political science professor at Panteion University in Athens, adding that voters may use the European parliamentary races to send a message to the Greek government. “People can vent their emotions in a protest vote.”