Sen. Lisa MurkowskiLisa Ann MurkowskiSinema touts bipartisan record as Arizona Democrats plan censure vote Kavanaugh impeachment push hits Capitol buzz saw McConnell lashes out at Democrats over 'unhinged' criticism of Kavanaugh MORE (R-Alaska) has invited supporters to a "campaign kick-off," according to a report, perhaps raising the prospect of an independent Senate run.

The Anchorage Daily News reported a Murkowski official invited supporters to "join us at the kick-off of Senator Lisa's campaign — with a theme of 'write in her name in and fill in the oval.'"

Murkowski is expected to formally announce this evening her intentions in the Senate race. She's been mulling a write-in campaign against Republican Joe Miller, to whom she lost the GOP nomination in the primary, and Democrat Scott McAdams. 

Hotline On Call reports she will run as a write-in candidate, "according to sources briefed on Murkowski's decision."

That would set up a three-way battle between her, Miller and McAdams. Hotline reports "private three-way polling has shown Miller leading, but by a narrow margin."

The National Republican Senatorial Committee put out a preemptive statement Thursday night discouraging Murkowski.

"If Senator Murkowski is truly committed to doing ‘what is right’ for her state, then we hope that she will step forward and fully endorse Joe Miller’s candidacy. No matter what Senator Murkowski decides for her own political interests in the future, Republicans are united behind Joe Miller’s nomination," spokesman Brian Walsh said.

Senate GOP leaders have said they support Miller and have discouraged Murkowski, a member of the leadership team, against running. Murkowski is also the top Republican member of the Senate Energy and Natural Resources Committee.

Murkowski's official announcement is expected around 9 p.m. EST.

-- This post was updated at 4:29 p.m.