Germans voted in a parliamentary election Sunday that is likely to award Chancellor Angela Merkel a third term leading Europe's strongest economy but may force the popular conservative to govern with her main center-left rivals.

The latest opinion polls show Ms. Merkel's Christian Democratic Union (CDU) securing nearly 40 percent of the vote while her pro-business partners, the Free Democrats, are rapidly losing support.

If the current coalition fails to win a parliamentary majority, the likeliest outcome is a switch to a Merkel-led partnership with the Social Democrats (SPD), led by her current rival, Peer Steinbrueck.

"I think it will be relatively tight because Peer Steinbrueck caught up in the end. My tip is on the grand coalition."

The recent surge of the Alternative for Germany - a new socially conservative party calling for an "orderly breakup" of the 17-member eurozone - could sap votes from both ruling parties, further weakening their chances of continuing the current government.

Nearly 62 million Germans are eligible to elect the lower house of parliament, which in turn chooses the chancellor.

Ms. Merkel formed a grand coalition with the Social Democrats in her first term that began in 2005. But if the Social Democrats win enough seats on their own in Sunday's election, they could form a coalition with the Greens and force her out of office.

If she stays in power, Ms. Merkel will become one of postwar Germany's longest-serving political leaders.

The election will be closely watched across the continent. In southern Europe - and especially, Greece - Germany continues to be vilified as the country that has forced austerity on the European Union, and many single out Chancellor Merkel.