Palin, in a Facebook post, said Miller has the "guts, wisdom, experience, and optimism to fight for what is right — and win."
Palin endorsed Miller, a tea party favorite, during his unsuccessful Senate bid in 2010. Miller upset Sen. Lisa Murkowski in the GOP primary that year, but Murkowski waged a historic write-in campaign to keep her job.
This latest endorsement comes days before Tuesday's contested primary, which also features Lt. Gov. Mead Treadwell and Dan Sullivan, whom Palin appointed as her attorney general in 2009 shortly before resigning as governor.
During a debate aired Thursday night, in which the candidates were asked what Alaskans, past or present, inspired them most, Miller cited Palin as being a "major inspiration" to Alaska, calling her a fighter and reformer. Sullivan said the late former U.S. Sen. Ted Stevens as an inspiration, and Treadwell cited the late former Gov. Wally Hickel.
Miller has spent much of the campaign painting his opponents as establishment types while casting himself as a "constitutional conservative" who would stand with the likes of Texas Sen. Ted Cruz and Utah Sen. Mike Lee and not compromise for the sake of political expediency. So it surprised some during the debate when Miller, who for months would not commit to supporting either Treadwell or Sullivan should he lose, changed his tune.
Miller said he believed he will win and would do everything he could to see that incumbent Democratic Sen. Mark Begich is defeated come November.
"But if one of you two guys, I've never said this before, I'll support you guys. I will," he said. "We've got to get rid of Begich. There's no question about it."
State GOP leaders, hoping to avoid a repeat of the divisive 2010 race and shore up their chances of defeating Begich, have been calling for party unity.
Miller spokesman Randy DeSoto did not directly answer a question about how the candidate reconciles saying he would support Treadwell or Sullivan, given his portrayal of them as part of the establishment.
"We intend to win, and Joe will not 'get along and go along' with the Washington establishment," DeSoto said by email.
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