Chris Cox, founder and leader of Bikers for Trump, is making the move from grassroots activist to Republican candidate by jumping into one of the hottest House races of 2020.

As he prepared to announce his run in South Carolina’s 1st Congressional District on Monday, Mr. Cox told The Washington Times that his biker brand and alliance with President Trump give him a distinct advantage in what is expected to be a brutal Republican primary.

“I’m very confident that we will be able to pull this off. It’s not going to be easy, but if you look at my past, you see that I don’t look for easy,” he said in an exclusive interview with The Times.

“I’ll tackle whatever is in front of me, and I’ll do it with a smile, I’ll do it with a calm, cool and collected demeanor, and I won’t let my emotions get the best of me,” he added later.

Don’t be surprised if you see Mr. Cox on the campaign trail wearing his trademark denim vest with the Bikers for Trump patches. However, he might replace the T-shirt, he said.

“I may have a collar on, but I’m not going to reinvent myself,” he said. “People need to see me and understand me as someone who gets things done. As far as trying to get a makeover, I don’t see that in my near future.”

Mr. Cox vowed to win back the longtime Republican seat from Democratic Rep. Joe Cunningham and use his clout as a Trump acolyte to work for residents in the district, which stretches along the state’s Lowcountry coastal region from Hilton Head to Charleston.

“What I would like to do is bring them a seat to the table and leverage my relationship with the president,” he said. “I’m sure Trump is going to win this election in 2020, and we need someone there who is going to be able to bring these federal funds back to Lowcountry.”

First, the chain saw sculptor turned grassroots activist turned congressional candidate will have to muscle his way through a bruising primary.

Mr. Cox joins three local politicians already in the race, and other well-known Republican figures are eyeing the contest.

The seat is considered ripe for a Republican takeover after Mr. Cunningham’s improbable win in November. The Democrat slid into the seat after Rep. Mark Sanford, a former governor and an outspoken Trump critic, lost the primary, perhaps wounded by a last-minute anti-Sanford tweet by Mr. Trump.

Katie Arrington won the Republican primary but stumbled in the general election against Mr. Cunningham.

Still, the South Carolina Republican Party is having a fierce debate about whether a Trump Republican would be the best candidate to win back the seat.

“It is going to be a positive in a Republican primary. That’s for sure,” said Katon Dawson, former chairman of the South Carolina Republican Party. “I don’t think they have to marry Donald Trump; they just have to date him a little while.”

Mr. Dawson said Mr. Trump’s popularity has grown in the district since he scored his narrowest victory over Hillary Clinton in the state. Now the economy is booming and Mr. Trump gets the credit, he said.

Others see Mr. Trump as a liability in the general election, where an influx of new residents has helped turn the district from red to purple.

“The key to me is to win the primary without selling their soul to Trumpism, which is going to be hard,” said Chip Felkel, a Republican Party strategist in the state. “In my view, Trump is, in this seat, likely not an advantage in the general. This is the coast, not upstate South Carolina.”

‘I want to get my hands dirty’

Mr. Cox’s political activism predates Mr. Trump and the biker organization. He first grabbed national attention during the 2013 government shutdown over Obamacare, when President Obama closed down open-air memorials in Washington.

Mr. Cox showed up carrying a South Carolina flag and pushing a lawn mower to cut the grass around the Lincoln Memorial. He said he was doing it for veterans.

He briefly became a TV news celebrity and was dubbed the “Lawn Mower Man,” a moniker he said he never liked.

In 2015, Bikers for Trump began as a fan club for the unconventional presidential candidate and then became the unofficial security detail for Trump rallies. Mr. Cox coined the phrase “wall of meat” to describe the biker brigade that stood between protesters and supporters at Mr. Trump’s events.

The organization grew into a grassroots political movement and put Mr. Cox on the front lines in support of pro-Trump House and Senate candidates.

He has turned over the day-to-day operations of Bikers for Trump to a top lieutenant but still plans to participate in events such as a Bikers for Trump ride in Israel from Tel Aviv to Jerusalem to mark the anniversary of the 9/11 attacks on the U.S.

Bikers for Trump has a large chapter in Israel, where Mr. Cox said support for Mr. Trump is among the highest outside the U.S.

He plans to hold a kick-off rally in the 1st Congressional District in September after the event in Israel.

Mr. Cox likely has the closest relationship with Mr. Trump of anyone in the race or thinking about running.

He has visited Mr. Trump in the Oval Office on several occasions. At the Independence Day celebration last week, Mr. Cox and about 30 other Bikers for Trump members had front-row seats for the president’s speech at the Lincoln Memorial.

Mr. Cox was born in South Carolina and his family has a long history in and around Charleston. He grew up in Northern Virginia, where his parents moved when he was a toddler because his father took a post in the Reagan administration.

He said he moved back to South Carolina after finishing high school.

Mr. Cox insisted that he has more going for him than the Bikers for Trump movement, though he is counting on a boost from the group’s roughly 80,000 active members across the country and 400,000 followers on social media.

“Bikers for Trump was turned into a political phenomenon,” he said. “But the base of my organization [in South Carolina] will be the reputation I’ve gained as a public servant — someone who is going to get the job done. No one is going to outwork me.”

He pointed to the breakneck pace he kept in the 2016 election when he toured the U.S. shadowing the Trump campaign and organizing Bikers for Trump rallies.

Although the White House is aware of Mr. Cox’s political ambitions, the candidate said he isn’t looking for Mr. Trump to deliver the seat to him.

“I’m going to go in here and fight for this seat just like anybody else. I don’t need any special help. I’m not looking for a tweet at this point — or anything. I want to get in here, I want to get my hands dirty,” he said. “I can win this on my own merits.”