Germans headed to the polls Sunday in federal elections that will decide in effect whether Angela Merkel should serve a historic fourth term as Chancellor.

Merkel’s center-right Christian Democratic Union, along with its Bavarian sister party, the Christian Social Union, appear to be heading to a handsome victory, according to eve-of-poll surveys. The two parties are expected jointly to win between 36 to 39 percent of the vote.

Germany’s second largest party, the center-left Social Democrats, who were junior partners in Merkel’s outgoing government, is likely to scrape just a 23 percent share, which if accurate would be the party’s worst electoral performance since 2009.

But the big question remained as voters braved a gray wet day to bring a three-month election season to an end: whether reactionary nationalists would enter Germany’s Bundestag for the first time since the Nazi era, marking a sharp departure for a country that has limits on political speech and is wary of any dramatic expressions of nationalism.

Pollsters are predicting the far-right Alternative for Germany will breach the five percent vote threshold required to gain seats, something it failed to do in 2013. Most analysts are expecting the AfD to secure ten percent of the vote — that would translate into 60 Bundestag seats, making the AfD Germany’s third largest parliamentary party.

Some analysts, though, are wondering if the AfD may garner more votes than have been forecast. They worry the party’s support may have been underestimated — especially in parts of west Germany like the industrial Rhur valley, once the center of German coal-mining and steel-making.

Helmut Jung, a consultant with the GMS polling agency, has warned of what he calls a high “non-disclosure quotient” among AfD-leaning voters, who may have hidden their true political preference. “The more the party is stigmatized as extreme rightwing, the more reluctant conservative voters are to admit that they support it,” Jung argues.

Pollsters have a history of underestimating AfD support. Before last year’s regional elections in Saxony-Anhalt AfD was forecast to attract support from 18 per cent of voters — instead the populists grabbed nearly a quarter of the vote.

Some analysts note that the AfD and its supporters have dominated social media, which may be a better gauge of the party’s growing strength. AfD drives more Twitter traffic than any other German party and it boasts more Facebook followers than either the CDU or Social Democrats.

In an interview with The Washington Post Sunday, AfD’s co-leader Alexander Gauland said the party’s fortunes had improved thanks to Merkel’s 2015 open-door policy for war refugees from the Middle East. “The ‘refugees welcome’ policy of Angela Merkel alienated a lot of people, a lot of voters, as you can see in the demonstrations against Merkel. We call it ‘Merkel muss weg’ demonstrations, or ‘Merkel must go,’”he said.

Asked about the surge in extremist violence against minority groups in Germany, Gauland said: “We have nothing to do with the extremism. We have nothing to do with violence against people.”

But critics accuse the AfD of providing a home for neo-Nazis and other extremists.

The emergence of the AfD as a parliamentary force would complicate Merkel’s choice of coalition partners if she is indeed victorious Sunday. She may decide to rule out inviting the Social Democrats to act again as junior governing partners in order to avoid the AfD becoming the official opposition in the Bundestag, say CDU insiders. Being designated the official opposition would give the AfD parliamentary privileges other parties would prefer to deny it.

That would force her to turn to the revived pro-market Free Democrats, who failed to secure any Bundestag seats in 2013, and the Greens in an arrangement being nicknamed the Jamaica Coalition because of the parties’ colors.

Both parties have recently formed coalitions with the CDU at the regional level but the Free Democrats are opposed to greater EU political integration and centralization, something Merkel has endorsed. Their leader, the 38-year-old Christian Lindner, has made it clear that he won’t budge on the issue of EU reform. “If we can’t make a difference, then it is our responsibility to go into the opposition,” he said recently.

Pressure is also building from within his party on Martin Schulz, the Social Democrats’ leader, not to enter into a coalition arrangement. Party insiders say that their election campaign floundered because they were unable to differentiate themselves from Merkel’s Christian Democrats.

Fearful of an AfD surge, Germany’s leading politicians across the political spectrum have been urging the public to come out to vote. Four years ago, 29 percent of Germany’s 61.5 million registered voters did not cast a ballot.

“Those who don’t vote let others decide the future of the country”, the country’s president Frank-Walter Steinmeier wrote in an article for the newspaper Bild am Sonntag. “Perhaps it has never been so noticeable that elections are also about the future and democracy of Europe,” he added.