ATLANTA (AP) — Herschel Walker said he "can't sit on the sidelines anymore” as he joined the Republican U.S. Senate race in Georgia. He's running with some definite advantages — including his football fame and the support of former President Donald Trump — but also with a lot of unknowns in his effort to beat Democrat Sen. Raphael Warnock in 2022.

“America is the greatest country in the world, but too many politicians in Washington are afraid to say that,” Walker said Wednesday in his first statement as a Senate candidate after filing to run Tuesday. “Where else could a poor kid from a small town in Georgia become valedictorian of his high school, earn the Heisman Trophy, play professional football, represent the United States in the Olympics, and become CEO of multiple companies? I have lived the American Dream, but I am concerned it is slipping away for many people.”

Walker faces some key questions: Will the first-time candidate prove to be a good politician and fundraiser? What will voters make of his sometimes troubled personal history? Can Walker lure back once-Republican moderates who have fallen away from the party, and peel off some traditionally Democratic African Americans?

Those hurdles could be harder to leap than the defenders the 59-year-old Walker overcame on his way to a Heisman Trophy as a University of Georgia running back in 1982.

“Herschel found it easy to run over linemen and defensive backs in the NFL," University of Georgia political science professor Charles Bullock said. "He's getting into a new game and may not have a lot of blockers out in front. I think he's going to find this is going to be a lot harder.”

If Walker emerges from the Republican primary, the Senate contest would feature two Black men vying for a seat in the heart of the Deep South. First, though, Walker has to get past Republicans already running, including state Agriculture Commissioner Gary Black, former banking executive and Navy veteran Latham Saddler and contractor Kelvin King.

One other potential opponent, Georgia Republican U.S. Rep. Buddy Carter, bowed out of a potential candidacy by endorsing Walker on Wednesday.

Walker dubbed his campaign committee Team Herschel in declaring his candidacy Tuesday with the Federal Election Commission. His foremost teammate may be Trump. Their relationship dates to the 1980s, when Walker played for a Trump-owned team in the short-lived United States Football League. Walker, who went on to play 12 seasons in the NFL, spoke in support of Trump at the 2020 Republican National Convention and later attended Trump’s private birthday celebration.

Trump publicly encouraged Walker to enter the primary, telling a radio show in June that “he’s a great guy, he’s a patriot and he’s a very loyal person, he’s a very strong person. They love him in Georgia, I tell you.”

With Trump the “defining figure” in today's GOP, Bullock said, the former president's backing might be all Walker needs.

“If he tells them they need to go out and vote for Herschel Walker, that's the strongest endorsement he can possibly get,” Bullock said.

But Trump's support could be a liability in a general election in closely divided Georgia.

“By the end of this long, divisive, and expensive intra-party fight, it’ll be clear that none of these candidates are focused on the issues that matter most to Georgians,” Georgia Democratic Party spokesperson Dan Gottlieb said in a statement.

Walker could share a Republican ticket with Gov. Brian Kemp, a frequent target of Trump attacks, as Kemp seeks reelection. Trump has vowed vengeance against Kemp, saying he didn’t do enough to overturn Trump’s election loss. It’s unclear if that enmity would damage Republican chances, with Democrats possibly fielding a united ticket of Warnock and Stacey Abrams. Walker endorsed Kemp, a fervent Georgia football fan, in Kemp’s 2018 victory over Abrams.

Warnock has already raised $10.5 million for the 2022 race but has downplayed Walker’s entry. He's now traveling the state promoting a jobs agenda.

“And I hear there’s a race next year,” Warnock told the Atlanta Press Club last week when asked about Walker.

Black has tweaked Walker for his long absence from Georgia, and did so again Tuesday in a video “welcoming” Walker to the race and challenging him to come to a Republican fish fry Saturday south of Macon.

“I suppose I’ve always wanted an autograph,” Black said, holding up a weathered football. “But there are some things that are far more important now: the future of our country, the future of our families.”

Sadler said in a statement that he's a better choice as a “next generation conservative leader who can beat Raphael Warnock.”

“This campaign isn’t about the glories of yesterday; it’s about our nation’s future," Sadler said.

Walker has been living outside Dallas and is making his first run for office. Walker is among Trump supporters who continue to repeat the president’s false claim that the 2020 election was stolen from him through fraud. Election officials nationwide found no widespread fraud.

Walker's past could also weigh on his campaign.

An Associated Press review of public records uncovered detailed accusations that Walker repeatedly threatened the life of his ex-wife, Cindy Grossman, by telling her relatives he would kill Grossman and her new boyfriend. Walker denied the accusations, but a judge granted a protective order in 2005 and for a time barred Walker from owning guns.

In 2008, Walker wrote a book that detailed his struggles with mental illness. He wrote that he'd been diagnosed with dissociative identity disorder, once known as multiple personality disorder. He said he constructed alternate personalities as a defense against bullying he suffered as a stuttering, overweight child. Walker was raised in Wrightsville, 50 miles (80 kilometers) east of Macon.

Walker also wrote of playing Russian roulette with a gun at his kitchen table in 1991. Overall, Walker cast his story as a turnaround, saying he found a path to “integration” because of therapy and his Christian faith.

The book caused problems for one of Walker's key business relationships. In a 2019 legal deposition, a manager for food distributor Sysco said the company almost cut ties with Walker's poultry company, Renaissance Man Food Services, when the book created “havoc.” Ultimately, Sysco stuck with Walker’s company until the controversy died down.

Walker has more recently made outsized claims about his business success. He repeatedly claimed his company employed hundreds of workers and grossed $70 million or more in annual sales.

But Walker’s company reported just eight employees when it applied for a federal Paycheck Protection Program loan last year. In a recent court case, Walker said his company averaged about $1.5 million a year in profit from 2008 to 2017.

State election officials opened an investigation into his wife’s residency after The Atlanta Journal-Constitution reported that records show Blanchard voted in Georgia despite living in Texas. Walker registered to vote last week at the Atlanta house Blanchard owns and registered his campaign Tuesday at the same address.

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An earlier version of this story incorrectly quoted Herschel Walker as saying he was “coming off the sidelines.” The correct version is Walker saying he “can't sit on the sidelines anymore.”

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Follow Jeff Amy on Twitter at http://twitter.com/jeffamy.