Kari Lake has formally filed to run for U.S. Senate in Arizona.

The conservative firebrand and ardent Donald Trump supporter had teased a run for weeks with expectations of a campaign launch for early October. National Republicans had initially been skittish on her candidacy after she lost the governor’s race in 2022 and launched a multi-month effort to challenge the validity of that vote.

But she has remained active in GOP politics since then, meeting with D.C. officials and staying particularly close to Trump. She spent Tuesday on Capitol Hill meeting with senators ahead of her expected launch next week.

Lake will enter the race as the heavy favorite to emerge from the GOP primary. But the general election is far less certain. Sen. Kyrsten Sinema (I-Ariz.) has hinted that she plans to run for reelection as an independent, while Rep. Ruben Gallego (D-Ariz.) has been campaigning for the seat for months.