Those activists also shrugged off comments McConnell made in an interview with the Weekly Standard, in which he appeared keen on ending the long-standing practice of giving senators a chance to block judicial nominees who would have jurisdiction over their states. Conservatives have been agitating for a more aggressive shaping of the bench in recent months.
Separately, an outside group affiliated with Stephen K. Bannon, the former chief strategist to President Trump who is waging a public war against McConnell and his allies, endorsed GOP Senate candidates in three states that were not objectionable to traditional Republicans.
The developments, coming in the middle of a week-long Senate recess, raised new questions about the trajectory of the intensifying war for the soul of the Republican Party and further blurred the battle lines within it. The complex struggle is expected to affect not only the midterm campaigns, but also the ongoing GOP attempt at a sweeping rewrite of the nation's tax laws.
In a letter to McConnell, six hard-right activists vented frustration with the Senate's lack of major legislative accomplishments this year, including its failure to undo the Affordable Care Act.
"It is time for you and your leadership team to step aside, for new leadership that is committed to the promises made to the American people," says the letter. The signatories did not immediately endorse a replacement for the job of majority leader.
Although McConnell is generally respected and well-liked by Republican senators, who determine their own leadership, some rank-and-file lawmakers have been hesitant of late to align themselves closely with him. In recent weeks, he has come under intense criticism from elsewhere in the party, including from allies and associates of Trump, most notably Bannon.
McConnell's job is not seen by Republican senators to be in immediate jeopardy, but the mounting attacks on him, which at times have come from Trump himself, have raised questions about his standing in the party.
Addressing reporters in a conference room inside the Capitol Hill office of FreedomWorks, a hard-right organization, five of the activists said that if McConnell does not step aside, they will wage an effort against him in next year's midterm elections that will take the form of television ads and other advocacy in individual campaigns where his allies are on the ballot.
"If Mitch McConnell does not step down, we foresee a scorched-earth disaster from a furious Republican base that will take it out on elected officials in 2018 and again in 2020," said Brent Bozell, the president of the Media Research Center. "It will begin simply by staying home — and rightfully so."
A McConnell spokesman did not have any immediate comment on the letter. It was signed by Bozell, Senate Conservatives Fund president Ken Cuccinelli II, Tea Party Patriots co-founder Jenny Beth Martin, FreedomWorks president Adam Brandon, For America president David Bozell and Richard Viguerie, the chairman of ConservativeHQ.com. They have all long clashed with congressional Republican leaders.
In his interview with the Weekly Standard, parts of which were published Wednesday, McConnell stressed that the use of "blue slips" — named after the piece of paper senators from a potential federal judge's state must sign to indicate their approval of his nomination — is a custom, not a rule, and that the use of them will no longer be enforced.
His comments came as he has endured increasing pressure from conservative groups. Politico reported this week that the conservative Judicial Crisis Network had planned to spend a quarter of a million dollars on ads pushing McConnell to more aggressively shepherd judicial nominees to passage, but his aides headed off the ad campaign.
"The majority," meaning Republicans, will treat blue slips "as simply notification of how you're going to vote, not as an opportunity to blackball," McConnell told the Weekly Standard.
In an interview with the New York Times last month, McConnell said that the Senate would no longer be observing the blue slip tradition for appeals court judges — arguing that it was not fair to allow just one senator to block progress on an appeals court judge with jurisdiction over several states if other senators from affected states were on board.
But the activists who held the Wednesday news conference were not very impressed.
"I'm glad that he's done that," said Martin. But she added: "Getting rid of the blue slip — it was time to do that a few months ago."
"No one in America has ever heard of the blue slip. That's a complete swamp thing," Brandon said.
McConnell cannot dictate the blue-slip policy shift on his own, and a spokeswoman for the majority leader urged against interpreting his comments too broadly. Taylor Foy, a spokesman for Senate Judiciary Committee Chairman Charles E. Grassley (R-Iowa) said that the senator has a tradition of using blue slips, and "expects senators and the president to continue engaging in consultation when selecting judicial nominees."
Meanwhile, the Bannon-affiliated group Great America Alliance endorsed Republican Senate contenders in three states: Rep. Marsha Blackburn in Tennessee; state auditor Matt Rosendale in Montana; and state Attorney General Patrick Morrisey in West Virginia.
Republicans aligned with McConnell did not take issue with the nods. All three are running for seats that are either open or are held by Democrats seeking reelection.
The three candidates have not pledged to oppose McConnell's leadership if elected, a stated priority for Bannon. And one of them has a campaign adviser whom Bannon has declared his enemy.
At a September rally produced by the alliance in Alabama, Bannon announced that Ward Baker, an adviser to Blackburn and outgoing Alabama Sen. Luther Strange, faced a coming "day of reckoning."
The broader coalition of candidates backed by self-described anti-establishment groups could suggest a more complicated 2018 playing field, with rival parts of the party working on the same side in some races. "Our 'Great America' slate, which will expand in the coming weeks, is entirely about delivering results," Eric Beach, the co-chair of the alliance, said in a release accompanying the endorsements.
One incumbent who appears to be safe from the hostility of Bannon and other conservative leaders bent on upending the makeup of the Senate is Sen. Ted Cruz (R-Tex.). Bannon and Cuccinelli have said they are not targeting him for defeat.
McConnell's inability to pass a bill in his chamber to repeal and replace the ACA as the GOP-controlled House did has made him a target of criticism among a growing number of Republicans. Trump has blamed him for the failure and voiced his disappointment publicly.
But the president has not called on McConnell to step down. Late last month, Trump expressed confidence in him.
Bannon, however, has more bluntly and actively opposed McConnell. The extent to which Bannon will be coordinating his efforts with the activists who spoke Wednesday is not clear, however.
"We are talking to many organizations, including Steve Bannon, about this," Brent Bozell said. The others who joined him did not specify how extensively they planned to collaborate with Bannon.