Democrats have, in the space of a few months, managed to pass a gun safety compromise, a major technology and manufacturing bill, a huge veterans health measure, and a climate, health and tax package — either by steering around Mr. McConnell or with his cooperation.
At the same time, the Supreme Court decision overturning Roe v. Wade appears to have handed Democrats a potent issue going into the midterm elections, brightening their hopes of keeping control of the Senate.
Mr. McConnell has acknowledged the challenges. He conceded recently that Republicans had a stronger chance of winning back the House than of taking power in the Senate in November, in part because of “candidate quality.”
The comment was widely interpreted to reflect Mr. McConnell’s growing concern about Republicans’ roster of Senate recruits, heavily influenced by former President Donald J. Trump and his hard-right supporters, who have earned Mr. Trump’s endorsement but appear to be struggling in competitive races.
It also hinted at a more basic problem that has made Mr. McConnell’s job all the more difficult: his increasingly bitter rift with Mr. Trump, which has put him at odds with the hard-right forces that hold growing sway in the Republican Party.
“Why do Republicans Senators allow a broken down hack politician, Mitch McConnell, to openly disparage hard working Republican candidates for the United States Senate,” Mr. Trump wrote in a social media post last month that also took aim at Mr. McConnell’s wife, Elaine Chao, calling her “crazy.” Ms. Chao served as transportation secretary in the Trump administration until she abruptly resigned after the Jan. 6 attack.
McConnell has had a nasty break with Senator Rick Scott of Florida, the chairman of the party campaign committee, who has styled himself in Mr. Trump’s image, recruited candidates loyal to the former president, visited him regularly in Florida and New Jersey, and this week attacked Mr. McConnell, without naming him, for questioning those candidates’ chances.
“Unfortunately, many of the very people responsible for losing the Senate last cycle are now trying to stop us from winning the majority this time by trash-talking our Republican candidates,” Mr. Scott wrote, calling such remarks “cowardice” and “treasonous.”