“We sensed the anger in ’13 and ’14,” Mr. McDaniel said in an interview at his law practice in downtown Laurel. “That anger,” he added, “reached its apex, it seemed, with Trump’s election. But now that McConnell and his merry band of yes men like Wicker have stood in the way of Trump, that anger has escalated again.”
“I’ve never seen this type of environment,” he concluded.
Mr. Wicker and his allies have not forgotten what happened in 2014 either, when Mr. McDaniel came within 3,500 votes of taking out Mr. Cochran. Mr. Wicker, the junior senator from Mississippi, has amassed a $3.1 million war chest and is doing everything he can to demonstrate how he — and not Mr. McDaniel — is the faithful defender of the Trump agenda.
“As much as Chris McDaniel may want it to be true, ‘Washington, D.C.’ will not be on the ballot for U.S. Senate in Mississippi next June,” said Justin Brasell, Mr. Wicker’s campaign manager.
“Senator Roger Wicker will be on the ballot,” he added, “the same Roger Wicker who traveled the country in 2016 working to defeat Democrats and elect Donald Trump.”
On policy, Mr. McDaniel and Mr. Wicker are not very far apart. They have both been supportive of Mr. Trump’s more controversial acts, like the travel ban on foreigners from predominantly Muslim countries. Both hold consistently conservative positions on gun rights and abortion. The biggest difference between the two is the matter of incumbency, which Mr. McDaniel hopes to turn into an unsurmountable liability for Mr. Wicker.
Mr. Bannon and the wealthy conservatives underwriting his campaigns believe that Mississippi offers a strikingly similar environment to Alabama, where Senator Luther Strange lost in a primary last month to Roy S. Moore, a former judge who built a large following as a champion of culturally conservative causes. The parallels are enticing: an incumbent close to Mr. McConnell, a well-known challenger with a political constituency of his own and a Republican base that feels betrayed because the party has yet to pass any major conservative legislation since taking control of both Congress and the White House.
Mr. Wicker’s allies argue that the Alabama race was more an anomaly than a rejection of Washington. Mr. Strange was viewed as ethically compromised by his perceived coziness with Robert Bentley, the former Alabama governor who appointed him to the Senate, then resigned under the threat of felony corruption charges.
Credit Al Drago for The New York Times
While some of Mr. Wicker’s colleagues have hedged their support for the president or are drawing attention to areas in which they disagree with him, Mr. Wicker is going all in. His Facebook page is full of photos that show him standing with Mr. Trump. Some do not even show Mr. Wicker — just the president. He also trumpets his “Trump Scorecard” of agreement with the president at 95.9 percent, ahead of conservative stalwarts like Senators Ted Cruz of Texas and Mike Lee of Utah.
But Mr. Trump may not end up being the most important person in the race whose name is not on the ballot. That could be Mr. McConnell, who has become the focal point for Republican grass-roots ire.
“If Mitch McConnell sends a lot of money down here for Roger Wicker just like he did with Luther Strange, I think it will backfire,” said Michael Bostic, a retired electrician and local Tea Party activist who said he believes Republicans have been giving lip service to campaign promises like repealing the Affordable Care Act. “I’ve tried to believe Republicans most of my life. But when they blatantly lie to you, that just doesn’t cut it.”
Mr. Bostic went to courthouses across the state to inspect voting records looking for evidence of fraud after Mr. McDaniel’s 2014 loss, and he said he believed that Mr. McConnell and his allies in party leadership had rigged that election.
“People are mad,” Mr. Bostic said.
Laura Van Overschelde, a local Tea Party leader, put it this way: “People are pretty hot under the collar. You can imagine the animus that still exists four years later.”
Mr. Cochran’s allies in the state and national party helped defeat Mr. McDaniel by using tactics that infuriated Tea Party groups. They encouraged African-Americans and other Democrats to vote in the primary. They went to great lengths to deny that Mr. Cochran was in an inappropriate relationship with an aide, Kay Webber, even as his wife, Rose, was in a nursing home with dementia. (Mr. Cochran married Ms. Webber not long after his wife’s death.)
After a Tea Party leader was charged with conspiring to photograph Rose Cochran in her nursing home, he committed suicide, triggering still more recriminations.
Mr. McDaniel refused to concede the race and fought the outcome for months in court.
“Remember Mississippi” became a Twitter hashtag and a slogan circulated on conservative email lists, and it is now the name of the “super PAC” supporting Mr. McDaniel, which recently received a $50,000 donation from Robert Mercer, the New York hedge fund investor who finances much of Mr. Bannon’s political activity.
If Mr. McDaniel runs, all of that bitterness is likely to return.
Beyond Mississippi, Mr. Bannon sees races in other states that he believes he and his coalition of conservative donors and activists can reshape next year. And in those states, Mr. Bannon said, he sees two common elements that work to the advantage of insurgent challengers: rural, deeply conservative populations and small, inexpensive media markets.
In Utah, he is plotting a challenge to Senator Orrin G. Hatch, another McConnell ally. Or if Mr. Hatch retires, as many expect, Mr. Bannon will take on the candidate that the party leadership endorses to replace him, which could be Mitt Romney.
In Wyoming, Mr. Bannon is pushing Erik Prince, the founder of the military contractor Blackwater, to run against Senator John Barrasso, a member of Mr. McConnell’s leadership team. In Nebraska, Mr. Bannon is interviewing candidates to run against Senator Deb Fischer. Bannon-backed challengers to Senators Dean Heller of Nevada and Jeff Flake of Arizona have already jumped in.
Mr. Bannon was also encouraged by Senator Bob Corker’s retirement in Tennessee, and the emergence of Representative Marsha Blackburn, a conservative firebrand, as the favorite to succeed him. Mr. Corker has said the president urged him to stand for re-election but that he has had enough.
Mr. Bannon insists otherwise.
“The biggest story is, Corker understands his career is over: six million in cash, chairman of the Foreign Relations Committee, which is by far the most prestigious in the Senate, and in Tennessee, which Trump won by 22 points,” he said. “We’ve got them on the run.”