Former Navy SEAL officer Eric Greitens declared Monday that he would run for the Senate seat being vacated by fellow Republican Roy Blunt. Greitens rose quickly to become Missouri governor before being forced out by controversy only a year and a half into his term.

Greitens, 46, made the announcement 14 days after Blunt said he would not seek re-election to a third term in 2022.

But even before Blunt’s announcement, Greitens had been setting the groundwork for a return to politics, with more regular appearances on conservative radio and television aimed at supporters of former President Donald Trump, who won Missouri with 57 percent of the vote in 2020.

In the heavily Republican state of Missouri, a number of other Republican candidates initially expressed interest in replacing Blunt, but the field is shrinking.

Lt. Gov. Mike Kehoe and early favorite Secretary of State Jay Ashcroft have both said they would not run, leaving Republican Attorney General Eric Schmitt and other members of Missouri’s congressional delegation as possible opponents for Greitens.

“My impression is that the Republican Party has sent a strong message to all potential candidates for Blunt’s seat that they want to focus their energies on one candidate, and a candidate who will be successful,” said Bill Hall, a political scientist at Webster University.

Blunt is the fifth Republican senator to say he will not seek reelection, a surge of retirements that could lead to a bruising campaign season next year and give Democrats renewed hope of keeping their Senate majority.

When Greitens ran for governor in 2016, he was a political novice with an impressive resume. He was a best-selling author, a Rhodes scholar, and the founder of a prominent charity for veterans in addition to his role in the elite military unit.

Greitens beat Republican establishment candidates in the primary and went on to win in November. Greitens was gaining attention as a possible presidential candidate by the end of his first year in office.

It all started to fall apart in January 2018, when a documentary about an extramarital affair with his hairdresser in 2015, before he was elected, aired on a St. Louis TV station. Greitens was charged for breach of privacy by a grand jury a month later, accusing him of taking a compromising picture of the woman and threatening to use it as revenge if she ever talked about the encounter.

Greitens admitted to the affair (he and his wife, Sheena, divorced last year), but denied criminal misconduct and accused Gardner, a Democrat, of pursuing the case for political reasons.

Gardner charged Greitens with another crime in April, accusing him of improperly using the donor list for his foundation, The Mission Continues, to raise funds for his 2016 campaign.

Meanwhile, the Missouri Legislature, which is controlled by Republicans, started debating whether or not to initiate impeachment proceedings. Greitens resigned in June 2018, ending the talks and the criminal charges.

His re-entry into public life has been slow. In 2019, he successfully applied for reinstatement to the Navy, but not as a SEAL officer. In the early days of the coronavirus pandemic last spring, he distributed masks to first responders throughout the state. He has his own internet and Dish TV show, and he appears regularly on conservative television and radio shows.

According to Ken Warren, a political scientist at St. Louis University, amid the controversies that forced him out of office, Greitens has strong support from around one-third of Missouri Republicans. If multiple establishment candidates siphon votes from each other, that support could be enough to win the primary.

“Republicans want to retake the Senate, and they need to keep Blunt’s Republican seat,” Warren wrote in an email. “Greitens would be a very dangerous Republican nominee because he could easily lose, even in Missouri’s red state.”

Marine veteran Lucas Kunce, former state senator Scott Sifton, and activist Timothy Shepard are among the Democrats running for the Senate seat.