Rep. Liz Cheney could face competition if she decides to run for the Republican nomination for Senate in Wyoming, with former Rep. Cynthia Lummis weighing a 2020 bid.

Lummis, 64, who retired from Congress in 2016 after four terms, is considering a political comeback in the wake of Republican Sen. Mike Enzi's decision to forgo reelection. Republicans close to Lummis said she would not be discouraged from running by Cheney, 52, whose failure so far to say whether she will make the race has otherwise frozen the field of potential candidates.

Cheney, Lummis' successor as Wyoming's at-large representative, is the daughter of former Vice President Dick Cheney, a beloved Republican in the state who held that same seat in the 1980s before being tapped as George H.W. Bush's defense secretary. That, and her position as the No. 3 ranking Republican in the House of Representatives, makes her the heavyweight in any potential GOP Senate primary.

Tucker Fagan, Lummis' chief of staff when she served in the House, told the Washington Examiner that his old boss is mulling a Senate bid and would make her decision irrespective of Cheney.

"She was a really good congresswoman for Wyoming," Fagan said. "She knows this state backwards and forwards, up and down. Her family has been in Wyoming for I can’t tell you how many years."

Enzi's retirement, announced last Saturday, caught Wyoming Republicans by surprise. Until then, Cheney was focused on her role as the House GOP Conference Chairman, essentially the conference's chief messaging strategist. Her colleagues have been impressed, and some party insiders say she could become speaker of the House the next time Republicans win the majority.

House Republicans are expecting Cheney to announce that she will run for Senate. If that's not her intention, some Republicans are urging her to quickly declare that she will remain in the House or risk squandering the goodwill and credibility she has amassed as a member of the House GOP leadership team.

"Time and patience eventually run out," said one House Republican, requesting anonymity in order to speak candidly. "It's just a question of how long it takes. She's fine now, but each week that will diminish."

[Opinion: A little-known name, not Liz Cheney, would be better in the Senate]