Update 8 a.m. Monday:
Alaska state Sen. Mike Dunleavy, R-Wasilla, on Monday announced he would resign his seat to "devote 100 percent of my time and energy to the cause of ensuring that Alaska elects a new governor in 2018."
"I've come to the conclusion that without new leadership in the governor's office, there is a practical limit to what any individual or caucus in the Legislature can achieve to turn this state around," Dunleavy said in a prepared statement that didn't explicitly say he would run for governor.
However, he announced in late December that he was resuming his run for governor after having suspended it because of a medical problem.
Mike Dunleavy, R-Wasilla, plans to announce Monday that he will resign from the Senate to run for governor, according to Republican Party Chairman Tuckerman Babcock.
[Wasilla Sen. Dunleavy resumes 2018 run for Alaska governor]
The senator, who represents a large district that stretches from Talkeetna to Valdez and Whittier, informed his local districts early Saturday and told his colleagues Saturday night at a fundraiser in Anchorage, Babcock said.
"He let people know that he would like to focus entirely on the race for governor," Babcock said.
[As state House members eye Dunleavy's Senate seat, Mat-Su assemblyman jumps into race]
It makes strategic sense for Dunleavy to resign now, because legislators are prohibited from fundraising during the legislative session that begins Jan. 16, Babcock said. Walker has also been apt to call special sessions, which would further limit Dunleavy's fundraising opportunities if he didn't step down.
Walker, an independent, announced in August he would seek re-election.
There are now five potential Republican candidates for governor including Dunleavy ahead of the state convention in March, Babcock said.
'We may well winnow the field at that point," he said.
The party will immediately begin taking applications for potential replacements for Dunleavy, Babcock said. After the senator makes his official announcement, Walker will have 30 days to select a replacement from up to three names forwarded to him by the party.
Correction: An earlier version of this story incorrectly said that Republicans had two weeks to forward names before the governor's 30-day consideration period.