Democrats Amy McGrath and Charles Booker, candidates for Kentucky's U.S. Senate race to oppose Senate Majority Leader Mitch McConnell in the November 2020 election. 

LOUISVILLE, Ky. (WDRB) – Amy McGrath, a former Marine fighter pilot whose well-funded campaign was backed by establishment Democrats, held off a challenge from progressive Kentucky state representative Charles Booker to win the Democratic primary for U.S. Senate. 

The Associated Press called the race for McGrath shortly before 12:30 p.m.

Booker had surged in recent weeks, mounting a charge during an unprecedented election during the coronavirus pandemic that allowed voters to cast absentee ballots by mail weeks ahead of the June 23 contest and vote in person. 

In some counties, there was a stark divide over voters' preferences on Election Day and in the runup to it, suggesting that McGrath may have benefitted from voters mailing their ballots before Booker's late push gained wide attention nationally and in Kentucky. 

McGrath will go on to face U.S. Senate Majority Leader Mitch McConnell in the November general election.

"I'm humbled that Kentucky Democrats have nominated me to take on Mitch McConnell in the general election and can't wait to get started in sending him into retirement and finally draining the toxic Washington political swamp that he built," McGrath said in a statement. 

She also congratulated Booker and said he "tapped into and amplified the energy and anger of so many who are fed-up with the status quo and are rightfully demanding long overdue action and accountability from our government and institutions."

And she called for Democrats to unify behind her and promised to "start the dialogue necessary to bring us all together in our common cause for the general election. There is far too much at stake."

The state's Republican party sought to contrast McGrath's bruising win with other GOP candidates' easier routes to victory. 

“Chuck Schumer’s hand-picked candidate Amy McGrath, who has called herself further to the left than anyone else in Kentucky, spent tens of millions of dollars to barely win a brutal and divisive Democrat Party primary,” said Sarah Van Wallaghen, the Republican Party of Kentucky's executive director. 

McConnell, President Donald Trump, and U.S. Reps Hal Rogers, Brett Guthrie, Thomas Massie, James Comer and Andy Barr all got "overwhelming support," she said. 

A decisive margin in Jefferson County was critical for Booker's hopes against McGrath, who racked up support from national Democrats, including Senate Minority Leader Chuck Schumer, and held a decisive fundraising advantage.

But Booker began climbing in the weeks leading up to the election. He appeared at Louisville protests over the police killing of Breonna Taylor, criticized the National Guard's presence in the city and received endorsements ranging from Kentucky state elected officials to Sen. Bernie Sanders and other progressives.

“We’ve proven Kentuckians are hungry for a new kind of leadership, one that puts working people and their struggles before corporate special interests and the corrupt politicians who serve them," Booker said in a news release Tuesday evening. 

“I want to be clear: this isn’t about me and Amy. I accept the results of this election, and concede this race. But we will push in the coming days to ensure transparency and accountability in our state’s electoral system, because it is essential that every single Kentuckian has faith in our democracy as we go forward."

Booker dominated his home county, receiving 88,116 votes to McGrath's 52,224. But the 35,892-vote buffer wasn't enough as other counties reported their results, and by early afternoon McGrath had pushed into the lead. 

As of 3:27 p.m., McGrath had taken 246,258 of all votes cast in person and through absentee ballots, or about 45.39%, compared with 231,502, or 42.67% for Booker, according to Associated Press results. All but 11 of Kentucky's 3,685 precincts had reported results. 

Mike Broihier, a self-styled outsider, was in third place with nearly 5% of the vote.

Click HERE for up-to-date election results.

Booker won Fayette County, the second-largest county in Kentucky, by a 3,515 vote margin ahead of McGrath, taking about 50 percent of the vote with all precincts reporting. He also won Christian County in southwestern Kentucky; Boyle County in central Kentucky; and Warren County, home to Bowling Green in the southern part of the state. 

McGrath won everywhere else; as of about 4 p.m. Tuesday, three rural counties -- Powell and Owlsley in eastern Kentucky and Hopkins in western Kentucky -- had not reported results. 

The results were released a week after the June 23 primary, which allowed absentee mail-in voting statewide because of the coronavirus pandemic. Gov. Andy Beshear, a Democrat, and Republican Secretary of State Michael Adams brokered the deal.

Roughly 218,000 of Jefferson County's 616,523 registered voters requested absentee mail-in ballots. By noon Monday, 185,365 of those had been returned, or about 85 percent. 

The Jefferson County Board of Elections reported Tuesday that 179,684 mail-in ballots were counted. Board spokesman Nore Ghibaudy said he didn't have data on how many ballots were rejected because they failed to provide the proper signature or for other reasons. 

Adams spokeswoman Miranda Combs tweeted preliminary turnout results as of 10 a.m. Tuesday, showing that 848,334 absentee ballots were returned and 274,363 Kentuckians voted in person. In all, 1,013,718 people voted, or about 29.2 percent of registered voters. 

Turnout in the 2016 presidential primary was 20.1 percent.

The Democratic primary also included nine other candidates, but the race for weeks was between McGrath and Booker.

McConnell easily won reelection in the Republican primary.

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