ANCHORAGE — Republican U.S. Senate candidate Dan Sullivan held an early lead over Democratic Sen. Mark Begich Tuesday night in Alaska’s hotly contested race.

Tens of millions of dollars were pumped into the high-stakes race, with Republicans seeing Begich as vulnerable. The number of early votes cast in the election, which included the governor’s race and a ballot measure to legalize marijuana, surpassed 2010, when there was another high-profile Senate race in Alaska, and the 2012 presidential race.

The GOP needed to pick up six seats nationally to regain control of the chamber and did so Tuesday, as polls were about to close in Alaska.

Begich, who was behind in results on election night in 2008, told supporters packed into an Anchorage restaurant that it would be a long night. “It might be a long week,” he said.

It was possible the outcome of the race may not be known until absentee ballots are counted next week.

Both Begich and Sullivan were out and about in Anchorage, waving signs and greeting supporters. Sullivan also got an unexpected call from his old boss, former President George W. Bush. Sullivan was an assistant secretary of state in the Bush administration.

In recent days, Texas Sen. Ted Cruz and former presidential candidate Mitt Romney were in Alaska to rally support for Sullivan. Begich shook hands with as many people as possible and deployed his wife and mother to outlying communities as part of his get-out-the-vote effort.

“How can you not feel good after something like that?” Sullivan said of the rally with Romney Monday that attracted a large crowd. “That’s energy. That’s Alaskans who are energized. You know, the Dems talk about ground game. We’ll see. That looked like a pretty powerful ground game to me yesterday.

Both sides felt good about their chances heading into Tuesday night. Democrats made an unprecedented investment in rural Alaska, while Republicans focused on shoring up support in the state’s most populous region.’

Sullivan, who stopped by Election Central in Anchorage as initial results began to come in, said it was far too early to speculate about a possible win by him. He said he wanted to thank Alaskans for their support.

Begich said he was confident he would wake up “it might be a week from now, two weeks from now, but we will be victorious.”

Begich played up his deep roots in Alaska — he was born and raised here, and his father was a congressman — while portraying Sullivan as an outsider prone to talking points. A leader in the Senate Democratic conference, Begich cast himself as an independent voice for Alaska, willing to work across party lines and unafraid to stand up to President Barack Obama. The tagline on his ads was “True Alaska.”

“I think people got fed up with the same old line from my opponent … he continued to talk about Obama, Harry Reid, you know, blah blah blah,” Begich said. “And what they saw with us, we talked about the issues.”

Republicans made the race a referendum on Obama and Senate Democratic leader Harry Reid, often citing that Begich voted with Obama 97 percent of the time. The figure referred to votes, many of them confirmations, on which Obama made his preference known in 2013.

Sullivan, whose roots in the state date to the 1990s, touted his family’s ties to Alaska. His wife is from here and his mother-in-law has been an Alaska Native leader. He also noted his work on energy and national security issues and efforts to combat sexual assault and domestic violence. He said this race was not only about the future direction of Alaska but the country.

Steady traffic was reported at a number of polling places in Anchorage, Alaska’s largest city. Several voters said they were glad the commercials and calls were coming to an end. Some also expressed disappointment with the tone of the race.

Justin Jurica, 37, called it a “mud-slinging war.” But he supported Sullivan, saying he generally agreed with what Sullivan stood for.

Piiyuuk Shields, 20, who is from rural Toksook Bay but studying elementary education major at the University of Alaska Anchorage, said it was important to support a candidate she thought would better defend subsistence-hunting rights for Alaska Natives. She voted for Begich.

“He’s been pretty good to us,” she said. “Why change what’s working?”