Karen Handel is in the middle of what Republicans see as a must-win race for Congress. And at a fundraiser on her behalf on Friday, President Donald Trump made sure she knew it.

At the closed-door event at the Capitol City Club, Trump turned toward Handel with a smile and quipped “you’d better win,” according to five attendees of the event. She responded that he need not worry about that.

The president has taken a deeply personal interest in the June 20 runoff between Handel and Democrat Jon Ossoff, a race to represent a suburban Atlanta seat that is widely seen as a test of his popularity.

Republicans have held the 6th District seat for decades, and Tom Price won it by a landslide in November before Trump made him his health secretary. But tepid support for Trump in the north metro district has buoyed Ossoff's campaign.

More: Handel gets help from Trump in Atlanta in 6th District race

Trump sent a barrage of tweets and recorded a robo-call last week urging Republicans to vote against Ossoff in the special election.

But he went a step further on Friday with glowing praise for Handel at a nationally-televised speech and a new attack on Ossoff at a National Rifle Association meeting in Atlanta. He followed that up with a private fundraiser for Handel afterwards.

Handel has embraced Trump right back. Although she did not run as a pro-Trump loyalist, she has increasingly relied on his support since her No. 2 finish in last week’s vote.

At the NRA event, Trump said Handel waged an "incredible fight" to land a No. 2 spot in last week's election and assure a matchup against Ossoff.

“She’s totally for the NRA and she’s totally for the Second Amendment. So get out and vote,” Trump said. “You know, she’s running against someone who is going to raise your taxes to the sky and destroy your healthcare.”

More: Trump tells NRA in Atlanta: I will ‘come through for you’

He struck a similar note at the Capitol City Club fundraiser, which attracted more than 100 Handel supporters who stroked checks of at least $2,600 to get in. Handel's campaign said it raised about $750,000 from the event.

Former U.S. Sen. Saxby Chambliss and U.S. Sen. Johnny Isakson – who once represented the district - warmed up the crowd before Trump spoke.

"He was chivalrous and he talked about the 6th District being Johnny's seat and Tom Price's seat. And then he joked that - with this legacy - you'd better win," said Mike Cheokas, a former state legislator who was among the attendees. "And he repeated it."

Cheokas drove up from Americus with a $2,600 check in hand at the request of Republican strategist Brandon Phillips, a former Trump campaign manager in Georgia who advised one of Handel’s rivals, Bob Gray, in last week’s race.

“It was nice seeing Karen embrace Trump,” said Phillips, who took the picture above. “I think that’s going to pay dividends for her. If Trump voters don’t turn out in June, that’s not good for us.”