Senate Minority Leader Mitch McConnellAddison (Mitch) Mitchell McConnellSenators near deal on sexual harassment policy change Blankenship third-party bid worries Senate GOP Overnight Finance: Trump signs repeal of auto-loan policy | Justices uphold contracts that bar employee class-action suits | US, China trade war 'on hold' MORE (R) is preparing a barrage of attacks against likely Tea Party challenger Matt Bevin, armed with what a senior campaign aide described “an opposition research book as thick as a college textbook.”  

Bevin, an investment firm executive and Army veteran, is expected to announce Wednesday he’ll mount a primary challenge against the five-term Kentucky senator. 

Jesse Benton, McConnell’s campaign manager, described Bevin as a “nuisance” candidate. 

“The welcome wagon's ready,” Benton told The Hill. 

The McConnell campaign’s confidence notwithstanding, Bevin’s expected entry into the Kentucky race this week is likely to complicate the senator’s reelection fight.  

It comes less than a month after Democrat Alison Lundergan Grimes launched her own bid to knock off the Senate’s top Republican. 

Bevin, 46, has met with a handful of conservative groups to discuss the Senate race. 

His candidacy has the potential to drain resources and time McConnell could otherwise spend targeting Lundergan Grimes, Kentucky’s secretary of state.

But Bevin will face a daunting task of his own: Convincing activists and donors he has the grassroots support and political skill to match McConnell, who is known for his take-no-prisoners brand of campaigning.

Benton said McConnell, who has $9.6 million in campaign cash, is capable of fending off challenges from the senator’s right and left flank. 

“We can walk and chew gum at the same time,” Benton said. “We can deal with this nuisance while keeping an eye on the bigger picture.”

For the moment, McConnell allies are taking a conservative approach to Bevin. 

Kentuckians for Strong Leadership, a super-PAC created to support McConnell’s reelection bid, said it has no plans to advertise againts the candidate.

The group has already spent more than half a million dollars in television ads attacking Lundergan Grimes. 

"We expect Bevin will be a speed bump on the way to the nomination for Senator McConnell,” Scott Jennings, a top adviser to the group and a former McConnell staffer, told The Hill in an email. 

McConnell, 71, has previously characterized his strategy for the early stage of his reelection campaign as “Whac-A-Mole.”

“When anybody sticks their head up, do them out," McConnell said in a private conversation caught on tape.

A slow trickle of negative press began before it was even clear Bevin would run. 

The Hill reported in March on Bevin’s inconsistent portrayal of his educational background and his affiliation with an investment firm that was embroiled in a trading scandal and fined hundreds of millions of dollars for improper conduct. Bevin said he was not involved in, and had no knowledge of, the misconduct. 

To be competitive, Bevin will need to gain the trust of Kentucky Tea Party activists who McConnell has spent months courting in anticipation of a primary challenge. 

The state’s biggest Tea Party star, Sen. Rand PaulRandal (Rand) Howard PaulSarah Sanders: ‘Democrats are losing their war against women in the Trump administration’ Kentucky Dems look to vault themselves in deep-red district Overnight Defense: Senate confirms Haspel as CIA chief | Trump offers Kim 'protections' if he gives up nukes | Dem amendments target Trump military parade MORE (R), has endorsed McConnell.

A number of Tea Party activists initially expressed skepticism about Bevin, noting he hadn’t been actively involved in Republican politics prior to floating a Senate campaign.

“We’re leery of outside folks coming in saying they’re Tea Party when they don’t have a Tea Party background,” John Kemper, spokesman for the United Kentucky Tea Party, told The Hill in February.

But the same Tea Party coalition released a letter on Monday indicating they are also opposed to McConnell. 

The letter from 15 Kentucky Tea Party groups addressed to two national Tea Party organizations urged the groups to withdraw their endorsements of the senator. The Kentucky activists said the national endorsements showed a “lack of research” and “poor judgment” about McConnell.

“Had you taken the time to reach out to us, you would have learned that the tea parties in Kentucky do NOT support Senator McConnell’s campaign,” Scott Hofstra, spokesman for the United Kentucky Tea Party, wrote in the letter. 

McConnell’s voting record — he has a lifetime 74 percent rating on the conservative Club for Growth’s scorecard — has long come under fire from Tea Party groups. 

McConnell has been criticized for voting yes on the last immigration overhaul, the financial bailout and previous debt-ceiling increases.

"I feel confident that Matt is a formidable candidate. As soon as [conservative groups] see how well he performs on the campaign trail, I have no doubt many of these groups will jump on board with him,” said one Bevin campaign aide, who spoke on background because the candidate has not yet officially entered the race. 

Bevin has also met with prominent national conservative groups, including the Club for Growth, the Senate Conservatives Fund and the Madison Project. 

Though Bevin is already spending thousands of dollars to advertise on-air in Kentucky, he’ll need their support to gain the legitimacy a Paul endorsement would’ve given him.

One conservative strategist who has spoken with Bevin described him as a “serious person” who will mount a credible campaign.

"Mitch McConnell will try to dismiss him, but if this were any other race, McConnell would be praising Bevin and calling him an outstanding recruit,” the strategist said.

Benton said the McConnell campaign plans to inform voters of Bevin’s background as “a chronic tax delinquent who fails to pay taxes and yet goes to government for handouts and bailouts.”

Bevin’s aide dismissed those attacks, calling them “normal Mitch McConnell” tactics.

“These are the same old tactics, the mudslinging he does every time. He's going to take half-truths or non-truths and try to make character assassinations out of them,” the Bevin aide said.

This story was updated at 7:10 p.m.