Former Wyoming Rep. Cynthia LummisCynthia Marie LummisSenate Republicans raise concerns about TSA cyber directives for rail, aviation Congress needs to step up on crypto, or Biden might crush it Senators preview bill to stop tech giants from prioritizing their own products MORE (R) on Thursday officially filed to run for outgoing Sen. Mike EnziMichael (Mike) Bradley EnziCheney on same-sex marriage opposition: 'I was wrong' What Republicans should demand in exchange for raising the debt ceiling Senate votes to end debate on T infrastructure bill MORE’s (R-Wyo.) seat in 2020.
Lummis, a former member of the conservative House Freedom Caucus, previously represented the Equality State as the state's lone House representative, but opted not to seek reelection in 2016.
Enzi, 75, in May announced his plans to retire from the upper chamber after serving 22 years.
Lummis is likely to face a difficult primary challenge, with many speculating House Republican Conference Chairwoman Liz CheneyElizabeth (Liz) Lynn CheneyAt least five Trump administration staffers have spoken with Jan 6 committee: CNN Juan Williams: Trump is killing American democracy Jan. 6 committee chair: 'No question' Capitol riot was a premeditated attack MORE (Wyo.) may opt to run for the position.
Former Wyoming Gov. Matt Mead, 57, has also been mentioned as a potential candidate in the race. Cheney, the No. 3 House Republican and the daughter of former Vice President Dick Cheney, previously sought to primary Enzi in 2014 before ultimately dropping her bid.
Lummis has not yet launched a campaign website or done media on her bid.
Bill Cubin, the treasurer of Lummis for Wyoming said despite the FEC filing to run, Lummis's camp said it doesn't constitute an official announcement.
"Cynthia will make an announcement regarding her plans in the near future. So, the news of the day, as far as Cynthia Lummis is concerned, is there is no news yet," he said in an email.
A GOP operative said to The Hill in a statement, “This looks like amateur hour. How do you file to run for office, without any campaign apparatus, but then claim you’re not actually a candidate?"
Sen. Rand PaulRandal (Rand) Howard PaulIt's time for Fauci to go — but don't expect it to happen On The Money — Democrats craft billionaire tax with deal in reach Rand Paul questioning if crypto could become world reserve currency MORE (R-Ky.) encouraged Lummis — who previously endorsed him for president — to run for the position, two sources confirmed to The Hill.
Lummis, a former cattle rancher, was considered by the White House as a potential contender to serve as Interior secretary in 2017.
Updated at 4:36 p.m.