Rep. Matt Rosendale (R-Mont.) on Thursday announced that he is pulling out of the hotly contested race for U.S. Senate in Montana after just a week.

Why it matters: It's a win for former President Trump and the Senate GOP's campaign arm, who both opposed Rosendale's candidacy.

What he's saying: In an unusually blunt statement, Rosendale pointed to Trump's endorsement of his establishment-backed opponent the day he launched his campaign as the key factor.

• "I have been forced to calculate what my chances of success would be with Trump supporting my opponent," the right-wing hardliner said.
• "By my calculations ... the hill was just too steep," he added, noting he was going up against both Trump and Senate Republican leaders.
• Rosendale said he made the decision in consultation with National Republican Senatorial Committee Chair Steve Daines (R-Mont.).

State of play: The decision leaves the GOP primary field essentially clear for businessman Tim Sheehy — considered by the NRSC to be the far stronger candidate against Sen. Jon Tester (D-Mont.).

• Trump endorsed Sheehy over Rosendale, but said he "also respect[s]" Rosendale and would endorse him if he opted to run for ree-lection.

Between the lines: The establishment pressure not to back Rosendale was so great that House Speaker Mike Johnson (R-La.) had to walk back a planned endorsement of the congressman following Senate GOP backlash.

What's next: Rosendale has until March 11 to decide whether to run again for his House seat, but a large Republican primary field has already formed.

• He said in his statement that he will "prayerfully consider what is next" over "the next few days" while home in Montana.