A brief timeline of the decline and fall of Matt Rosendale:

Feb. 8: Mike Johnson endorses/unendorses Rosendale within a few hours.
Feb. 9: Files to run for U.S. Senate anyway
Feb. 15: Withdraws from race, citing Trump's endorsement of Tim Sheehy.
Feb. 26: Former Senator Heidi Heitkamp states the rumor that Rosendale had impregnated a 20-year-old intern in his office and will soon be leaving congress.
Feb. 27: Rosendale denies the rumor and threatens legal action (that never happens)
Feb. 28: Vows to continue running for his congressional seat in Montana's second district.
March 8: Rosendale leaves the race, citing some bullshit or other that I can't be bothered to read, and leaves the race before the March 11 filing date for MT-02.

Rosendale says he'll serve out the remainder of his term but if it's like any of his other promises, that's probably just as meaningless.

Source: CNN

Republican Rep. Matt Rosendale of Montana announced Friday he is not seeking reelection to his US House seat, citing “defamatory rumors.”

Rosendale briefly ran for the Republican nomination for a US Senate seat in the state, but dropped out after one week when former President Donald Trump endorsed retired Navy SEAL Tim Sheehy.

On February 28, Rosendale said he would run for his House seat again but has now decided not to seek reelection.

Rosendale said that he had sought help from law enforcement following death threats, as well as “false and defamatory rumors against me and my family,” following his reentry into the US House race.

“The current attacks have made it impossible for me to focus on my work to serve you,” Rosendale said in his statement. “So, in the best interest of my family and the community, I am withdrawing from the House race and will not be seeking office.”

And Rosendale's exercise in creative writing.