(CNN) – With Alaska's U.S. Senate seat considered one of the most vulnerable Democratic seats this fall, both Republicans and Democrats have a lot at stake in Tuesday's GOP primary.
The winner of the crowded race will square off against incumbent Democratic Sen. Mark Begich in November. Republicans, who need a net win of six seats to retake control of the Senate, have focused on the contest in the traditionally red state of Alaska as a key turnover possibility
Dan Sullivan, former natural resource commissioner and former state attorney general, is considered the Republican frontrunner due to his sizable fundraising advantage and steady lead in recent polls.
He's running against Lt. Gov. Mead Treadwell and attorney Joe Miller, the latter of whom has strong backing from tea party supporters. Miller is also known for defeating incumbent Sen. Lisa Murkowski in the 2010 GOP primary. But Murkowski ultimately won the general election with a write-in campaign.
Begich's allies have been aggressive in the race, pouring millions into ads that mostly target Sullivan, the Republican who could be the most competitive against Begich in the general election.
Sullivan's critics have zeroed in on his residency in Alaska. While the candidate has lived and worked in the state, he's originally from Ohio and didn't live in Alaska for a chunk of time last decade when he worked in the George W. Bush administration and in the military.