U.S. Sen. Pat Roberts' announcement Friday that he will not seek re-election in 2020 could open the floodgates in Kansas for a slew of Republican candidates looking to serve in Washington.

The GOP primary to replace Roberts could pit outgoing Gov. Jeff Colyer and U.S. Rep. Roger Marshall, the Kansas City Star reported. Colyer's re-election hopes were dashed when he lost to Kansas Secretary of State Kris Kobach in the Republican gubernatorial primary. Kobach was ultimately defeated in November by his Democratic opponent, Gov.-elect Laura Kelly, who will take office Jan. 14.

“There’s only two U.S. Senate seats from Kansas. They’re not making anymore,” David Kensinger, a longtime GOP consultant who has previously managed Senate campaigns for both Roberts and former Gov. Sam Brownback, told the Star.

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Marshall is the state’s most senior member of the U.S. House of Representatives and has been considering a run in recent weeks amid speculation that Roberts would not seek another term, Politico reported.

"Since the moment speculation of Senator Roberts' retirement began, Dr. Marshall's phone has been ringing," Brent Robertson, Marshall's chief of staff, said in a statement. "It's safe to say that while Dr. Marshall is seriously considering it, he is dead set on making sure we get border security funding to the President's desk first. Until then, I don't anticipate any type decision on a Senate run taking priority."

Also weighing a run is state Attorney General Derek Schmidt.

U.S. Secretary of State Mike Pompeo’s name also was mentioned Friday as a potential candidate.

Pompeo previously represented Wichita in the House of Representatives from 2011-17. But sources close to him told the Star that he’s focused on his current role.

“I’m sure that he will be flattered to be mentioned, but I’m also sure that he is focused on doing his job as secretary of state and ensuring the safety and security of every Kansan,” the source said.

Kelly Arnold, chairman of the Kansas Republican Party, sees Colyer, Marshall and Schmidt as the most likely candidates.

Other names being floated include former Kansas Rep. Kevin Yoder, who lost his seat to Democrat Sharice Davids, Matt Schlapp, chairman of the American Conservative Union, who grew up in Wichita, and Ajit Pai, the Kansas native who chairs the Federal Communications Commission, Arnold said.

Kansas Senate President Susan Wagle may also contemplate a run, the paper reported.

Scott Paradise, a GOP consultant, warned that the crowded field could elevate a candidate unable to win in the general election.

“We lost the governor’s mansion because we had too many candidates in the primary, which left us with a divisive nominee that didn’t raise money or work hard enough,” Paradise told the paper in a text message. “It’s important that doesn’t happen again.”

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Following Roberts' announcement, the state Democratic Party sent out a fundraising email. Its field of candidates is relatively small at the moment.

Roberts declined to single out anyone as his possible successor before joking that Bob Dole, the 95-year-old former senator from Kansas, could run again.

“I love Bob. Bob loves me. Just had a conversation about it. He says ‘You’re sure you’re giving this up?’ I said ‘I think so, Bob, I think it’s time. So that means there’s an opening.’ He says ‘I might consider that,’” Roberts said. “So write that down, that Bob Dole might come back and run for the Senate.”