Sweden is heading to the polls in a closely contested general election that could see the center-left opposition return to power or the far-right Sweden Democrats enter government for the first time.

Prime Minister Ulf Kristersson and his right-wing alliance are facing a challenge from a four-party opposition bloc led by former Prime Minister Magdalena Andersson, leader of the Social Democrats.

Opinion polls had initially indicated a comfortable advantage for the opposition. However, that lead has narrowed in the final days of the campaign, turning the election into a tight contest.

“We all knew it was going to be a very close election,” Andersson told supporters at a rally in Stockholm on Saturday. She urged voters to choose between a government led by her Social Democrats and one in which the Sweden Democrats would have significant influence.

The Sweden Democrats, led by Jimmie Åkesson, have emerged as a major force in Swedish politics since first entering parliament in 2010. Unlike Germany's political parties, which have largely maintained a firewall against the far right, Kristersson has indicated that the Sweden Democrats could receive key government positions if his alliance wins.

Åkesson told a campaign rally in Stockholm that his party had “already won” and said Sweden was becoming “safer, better, and more Swedish.” He is expected to seek the position of migration minister if the right-wing alliance forms the next government.

The Social Democrats, who have dominated Swedish politics for much of the past century, remain the country's largest political party and are seeking to return to government after four years in opposition.

Around eight million people are eligible to vote in the election, in a country of approximately 10.6 million inhabitants. Voter turnout in Sweden traditionally exceeds 80 percent.

Polling stations are scheduled to close at 8 p.m. local time (1800 UTC), with initial results expected later on Sunday evening. About half of the votes have already been cast through advance voting.

The outcome could mark a significant shift in Swedish politics, particularly if the Sweden Democrats gain formal government power for the first time.