Updated 2:57 p.m. | Former Rep. Cynthia Lummis announced Thursday she is running for the open Senate seat in Wyoming, officially jumping into what could turn into a crowded Republican primary.

Longtime GOP incumbent Michael B. Enzi announced in May he would not run for re-election. Whoever wins the GOP primary would be the favorite to replace him given the state’s strong Republican lean.

“I’m ready to stand shoulder-to-shoulder with President [Donald] Trump to ensure conservative voices are heard loud and clear and to deliver real results for Wyoming people,” Lummis said in a statement.

Lummis filed to run for Senate in June, but made her campaign official with her Thursday announcement. She has worked on her family’s ranch since deciding not to run for a fifth term to the House in 2016. She said Thursday that she “can’t in good conscience watch from the sidelines as our way of life is threatened by liberal ideologues in D.C.”

Lummis served two terms as state treasurer between 1999 and 2007, and also served in the state House and Senate prior to that. As a congresswoman, she was the lone female member of the hard-line conservative House Freedom Caucus. 

The Senate GOP primary is expected to be crowded, and could include current Rep. Liz Cheney, who succeeded Lummis in the House and now serves as the chamber’s GOP conference chairwoman. 

Lummis told reporters on a conference call Thursday afternoon that she spoke to Cheney recently and informed her that she would be running for Senate.

“This is Wyoming’s seat, and I’m not running for this race having predetermined who else might get in this race,” Lummis said. She also said that if Cheney did get in the race, the primary would be a “real barn burner.”

Lummis said she is more libertarian than Cheney, especially when it comes to international intervention. The former lawmaker also noted that both Cheney and Wyoming’s junior senator, John Barrasso, are members of congressional Republican leadership, and argued it would benefit the state to have a member of their delegation who is not and “can take leadership on.” 

“I played that role when I was in the House,” she said, noting that she was removed from the whip team while in the House over a procedural vote on a trade bill.

Two Democrats have filed for Enzi’s seat. But the party hasn’t won a Senate race in Wyoming since 1970, and it hasn’t seriously contested one since Enzi won his first term in 1996, defeating former Wyoming Secretary of State Kathy Karpan. He won his most recent re-election in 2014 by 55 points, while Trump carried the state by 46 points in 2016.

Inside Elections with Nathan L. Gonzales rates the Senate race Solid Republican.