A man walks past the placard of German Chancellor Angela Merkel, left, and her challenger Peer Steinbrück on September 20, 2013 in Berlin. A total of 61.8 million people over the age of 18 will be able to vote on Sept. 22 to elect the next government of the European Union's most populous nation and biggest economy. (John Macdougall/AFP/Getty Images)

Chancellor Angela Merkel’s center-right party appears poised to win Sunday’s elections in Germany, which would put her in place to become one of postwar Germany’s longest-serving political leaders.

If polls prove accurate, Merkel, 59, would win another four-year mandate to lead Europe’s most powerful economy. Her top challenger, center-left candidate Peer Steinbrück, spent his final days on the road trying to convince voters that Merkel has failed to exert real leadership in Germany since she was first elected in 2005.

The campaign has been marked by controversy over U.S. spying on European soil and dust-ups over whether German society is becoming less fair to its most vulnerable groups. It remained unclear who might emerge as Merkel’s coalition partner.

If Merkel were to serve another four years at the top of her political system, her longevity in office would lag behind only Konrad Adenauer, the man who rebuilt Germany after World War II, and Helmut Kohl, Merkel’s political mentor, who oversaw the reunification of West and East Germany.

Merkel has presided over a transformation that is in some ways nearly as remarkable, commentators say. Under her watch, Germany has evolved into the undisputed economic leader of Europe, a country that has used its power over struggling countries to push for fundamental reforms and greater austerity. At the same time, Germany has remained deeply skeptical of the value of foreign military interventions, sitting out the NATO action in Libya two years ago and, at least for a while, holding back this month from signing on to an international condemnation of Syrian President Bashar al-Assad for his regime’s alleged use of chemical weapons in August.

With polls showing Steinbrück’s Social Democrats and the party’s preferred coalition partner, the Greens, lagging behind Merkel’s current coalition, the biggest question as voters head to polling booths appears to be whether Merkel will be forced to seek a cross-aisle alliance with the Social Democrats if her current pro-business partners, the Free Democrats, lose too much support. If she teams up with Steinbrück, Germany would be pulled leftward after four years in which it has been Europe’s austerity taskmaster, although few here expect a fundamental reimagining of the country’s approach.

Whoever wins will face a host of thorny issues that Merkel’s Christian Democrats have postponed for much of the year, analysts say. Tough negotiations to resolve Europe’s simmering currency crisis have been on hold, and further assistance for Greece, as well as possibly another debt write-off, may come within months. If Steinbrück’s Social Democrats share power with Merkel, she could be forced to be more hospitable to common European government borrowing, which the Social Democrats have advocated.

At home, the issues are no less tricky, despite unemployment that touches post-reunification record lows. German energy costs are soaring because of ambitious plans to increase the share of renewable energy and phase out nuclear power. Infrastructure is aging, and Germany invests significantly less than its neighbors in upkeep. And the population is growing older, meaning that Germany’s prized social-welfare benefits are increasingly floating on an ever-smaller cushion.

Steinbrück, 66, a witty candidate whose penchant for saying whatever is on his mind has gotten him into trouble on the campaign trail, has focused his electioneering efforts on what he has characterized as Merkel’s deferred decisions.

“She doesn’t provide direction for this country. She likes to drive in circles,” Steinbrück told a cheering crowd of several thousand in Berlin’s Alexanderplatz this past week. On Sunday, he told them, “you’ll have the opportunity to bring about a change of government.”

Merkel, meanwhile, has promised voters more of the same. Unemployment has dropped from 11.3 percent when she took office in 2005 to 5.3 percent today, declining even through the global economic crisis in 2008. The economy is growing.

“We have to ask ourselves: How can we make sure that this will continue in Germany? At present we have got more people in jobs than we’ve ever had. But this can also quickly be destroyed,” Merkel said at a rally in Munich on Friday, adding that Germany should not engage in any “experiments.”

“She is very popular, a different type of politician, a politician whose rhetoric isn’t so great but who gives arguments, who tries to win by persuasion,” said Jürgen Falter, a professor of political science at the University of Mainz.

Steinbrück, by contrast, “is a totally different type of person,” Falter said. “He describes himself as a clear-cut, outspoken politician who doesn’t hide anything. His tongue is sometimes faster than his thinking.”

The wild card in the election is the new, anti-euro Alternative for Germany party, which has been polling just below the 5 percent threshold necessary for it to enter Parliament. Until now, Germany has not had a right-wing, nationalist party in the mainstream, unlike many of its European neighbors. The group also favors immigration restrictions and says it wants to lure only skilled labor to Germany, although it takes pains to distance itself from the nationalist parties in other countries whose policies verge on racist.

If the new party makes the cut, analysts say, there will be a focus on the views of the sizable minority of Germans who think the euro has not had a positive effect on their country.

“They will be able to express their political positions more than before, because they’d get some media exposure,” said Oskar Niedermayer, a professor of political science at the Free University of Berlin. “But they will not have any real influence on government.”