Originally Published: 23 MAY 22 00:05 ET

By Manu Raju and Alex Rogers, CNN

(CNN) -- Last summer, Senate GOP leader Mitch McConnell was nervous about Herschel Walker, seeing stories about the rookie candidate's turbulent past and fearful that an unvetted and untested Republican could implode in the heat of the biggest Senate race in the country.

But not long after he suggested to allies that former Georgia Sens. David Perdue and Kelly Loeffler should consider running, McConnell heard a different story -- from Walker himself. Over the course of multiple conversations, Walker and McConnell talked about the campaign, the candidate's life story and the GOP leader's view of running in a race like this, according to people familiar with the calls.

"I think this guy is the real deal," McConnell said to Sen. Lindsey Graham last fall, according to the South Carolina Republican, who had been lobbying the GOP leader to get behind Walker, a football legend with the support of former President Donald Trump.

Since then, Walker has had a cakewalk of a primary, skipping a handful of debates or forums, avoiding getting pinned down on policy positions and mostly limiting press appearances to the safe spaces of conservative media. In mid-May, a Fox News poll showed Walker with 66% support from Georgia Republican primary voters -- unchanged since March.

But after his expected blowout victory in Tuesday's primary, the scrutiny is only bound to intensify. Democrats are privately planning an aggressive campaign spotlighting Walker's vulnerabilities, business record, policy views and dirty laundry about the candidate's past, including his violent behavior with his ex-wife, according to a source familiar with the matter.

Walker has said he has dissociative identity disorder, which was previously known as multiple personality disorder, and has sought to advise people with mental health problems.

In 2008, his ex-wife claimed that he threatened her life, pointing a gun to her head a handful of times and a straight razor to her throat; Walker said in an interview that year that he didn't remember being violent toward her, but he didn't deny it and noted that one of the symptoms of his disorder was blackouts.

In 2012, an ex-girlfriend told authorities that Walker had also threatened to kill her and "blow her head off" and then "blow his head off." After the allegation was reported last year, Walker's spokesman said the candidate "emphatically denies these false claims."

And a third woman also said Walker threatened and stalked her in 2002. Walker's campaign previously declined to respond to the woman's allegations or discuss the police report.

Top Democrats believe that Walker will collapse as the fight between freshman Democratic Sen. Raphael Warnock and Walker intensifies.

"I don't think he is ready for prime time," said Michigan Sen. Gary Peters, the chairman of the Democratic Senatorial Campaign Committee. "I don't think he understands the significant policy issues that we face as a country. And what he does believe in is simply not going to resonate with the voters of Georgia. So he's going to make every effort he possibly can to hide from the voters of Georgia."

"Who is he hiding from? Sen. Warnock's out there every day answering questions and showcasing his extraordinary work delivering for the state," Georgia Democratic Sen. Jon Ossoff said. "A candidate who's hiding from the public is afraid."

Republicans scoff at that notion.

"They don't know what they're talking about," Graham, who has been advising Walker and met with him in Georgia last month, said of Democrats. "This is a referendum on (President Joe Biden's) policies. Just keep it focused on 'If you want a rubber stamp of the most destructive policies in modern American history, vote for that guy. If you want to stop this craziness, vote for me.'"

And his advice to Walker? "Be yourself. Tell your story."

Asked about Walker's past problems in an interview earlier this year, McConnell told CNN: "I looked into Herschel Walker's record -- I'm entirely comfortable with him."

While the Walker campaign did not respond to a request for comment on the attacks Democrats plan to launch against him, a Walker aide noted that the candidate has spoken with every senator who has endorsed him.

Skating through the primary

Walker's allies reject the notion that he's been hiding, pointing to events he has had throughout the state. Yet Walker's Republican opponents in the Senate race have accused him of just that.

A recent debate between Georgia Agriculture Commissioner Gary Black, retired Navy SEAL Latham Saddler, construction company owner Kelvin King, former state Rep. Josh Clark and Army veteran Jon McColumn turned on the same question: Where is Herschel?

Black, Walker's top GOP rival, tweeted on May 17 that Walker "refuses to debate the issues much less discuss his past. It's a pattern of deflect, defer, run, hide, and twist. It's unacceptable for service in the U.S. Senate." Black then told The Atlanta Journal-Constitution that he would not support Walker as the nominee because "anybody who has put his hands on a woman like he has and has not taken responsibility has not earned my vote."

Walker defended himself in an interview with Atlanta's Fox affiliate last week. Walker said that Black is attacking him because the state agriculture commissioner is losing, that he is not currently receiving treatment for mental health and that he wants to help those with similar mental health issues if he serves in Washington, and that he and his ex-wife are close.

"And if it wasn't for her, I wouldn't be the person I am today," he said. "Right now, I think people can bring up all the past. But the past is the past."

While Black has raised some of the same concerns that McConnell once had, and that Democrats are sure to try to exploit, Black has not had the resources to air his attacks against Walker. Black has spent about $213,000 on ads in the primary, according to AdImpact data. Warnock has already spent or reserved more than $30 million in ads for the race, while the Senate Majority PAC, a liberal super PAC, and the DSCC have reserved another $30 million-plus to help him.

Warnock himself has not yet attacked Walker. Asked about his likely opponent last week, the senator told CNN he's focused on trying to pass a bill to cap the cost of insulin.

"I do a lot of hard work for folks in Georgia," Warnock said.

Walker, however, also has a number of advantages in the race, including Biden's underwater approval rating, the historical benefit of running in a midterm election against the party in power, and a host of issues -- from rampant inflation at home to global crises abroad -- that damage Democrats up and down the ticket.

Warnock wouldn't say whether he would want Biden to campaign for him.

"There will be plenty of time to talk about that," he told CNN.

But Republicans believe that if Walker can keep the focus on the Biden agenda, that could be enough to win in an election environment that favors their party.

"I see him out there all the time," Florida Sen. Rick Scott, the chairman of the National Republican Senatorial Committee, said of Walker. "He's going to win."