For months, Democrats saw Amy McGrath, a retired Marine Corps fighter pilot, suburban mother of three and moderate with no Washington ties, as the ideal candidate to wage a long-shot bid to unseat one of the most powerful men in Washington: Senate Majority Leader Mitch McConnell (R-Ky.).

But that was before everything changed.

It was before the coronavirus pandemic exposed the nation’s deep racial health inequities. It was before George Floyd, a black man, died under a white police officer’s knee, sparking protests nationwide over police brutality and racial injustice. And it was before a little-known state representative named Charles Booker seized the moment of national reflection and upended the Kentucky Democratic primary.

McGrath, 45, had been courted by national Democrats to run, raised more than $41 million and has more cash in her campaign account than McConnell, with Republicans already targeting her with attack ads. Now she finds herself immersed in a heated and competitive race, with the primary Tuesday.

Booker, a 35-year-old African American who grew up poor, sometimes homeless, in urban Louisville, marched with protesters in more than a display of solidarity. He marched for his four cousins who had been murdered, and for Breonna Taylor, 26-year-old medical worker killed by Louisville police executing a no-knock drug warrant. Taylor had no prior drug convictions or arrests, and no drugs were found in her home.

Booker said Taylor, whose death triggered days of protests, was a family friend.

“The trauma is very real and the sense of feeling invisible and feeling like no one hears you and or cares about you is very real, and that’s why you see people take to the streets,” Booker said in an interview.

The endorsements came swiftly. First from Sen. Bernie Sanders (I-Vt.) and Rep. Alexandria Ocasio-Cortez (D-N.Y.). Then both of the states’ major newspapers. This week Sen. Elizabeth Warren (D-Mass.), who a year ago had tweeted, “Go Amy!” when McGrath entered the race, publicly endorsed Booker.

The Holy Grail of political upsets for Democrats would be unseating McConnell, 78, who is seeking his seventh term. The Republican leader relishes the moniker of “grim reaper” for blocking legislation passed in the Democratic-led House, hardly ever challenges President Trump and has ensured confirmation of 199 of the president’s judicial nominees in remaking the courts for years.

Democrats still seethe over McConnell’s refusal to consider President Barack Obama’s Supreme Court nominee Merrick Garland in 2016.

Most of the money that has poured into McGrath’s campaign is from out-of-state Democrats — similar to what happened in 2018 to former congressman Beto O’Rourke in Texas when it looked like he had a chance of ousting Sen. Ted Cruz, another GOP senator loathed by Democrats.

It would be a herculean feat to defeat McConnell in a presidential election year in a pro-Trump state that the president won in 2016 by 30 points. Although McGrath has raised tens of millions of dollars, McConnell has raised more than $26 million, has more than $15 million cash on hand and the Senate Leadership Fund, a Republican super PAC, has reserved $10.8 million in Kentucky.

Not only is McConnell fighting for another term, he is battling to keep his Senate GOP majority. The party holds a 53-to-47 advantage but has vulnerable incumbents in Maine, Colorado, Arizona and North Carolina as it defends 23 of 35 seats.

McGrath supporters argue that with an opponent such as Booker, who embraces a liberal platform that includes the Green New Deal environmental plan and Medicare-for-all, it would be impossible to defeat McConnell.

“Booker would be a long shot against McConnell, but he makes the point that he’s the candidate of the fed up. There’s a lot of people out in rural Kentucky who are fed up, too; his argument is that there are plenty of people out there who want to shake up the system,” said Al Cross, a professor at the University of Kentucky and political columnist, who said McGrath would also have an “uphill battle.”

McGrath has focused much of her attention on McConnell, using her “On Duty with Amy McGrath” podcast to criticize the GOP leader’s resistance to sending federal money to states in a new round of economic aid during the recession. She also has highlighted the importance of education as teachers played a critical role in helping Gov. Andy Beshear (D) defeat Republican incumbent Matt Bevin last year.

Her most recent podcast addresses systemic racism. “People are calling for a new generation of leaders who will work to tackle the economic, social and education inequities that prevent true racial equality,” she said.

But before either Democrat faces McConnell, one of them has to win Tuesday’s primary in an unprecedented environment. Amid an ongoing global pandemic, the state is allowing all voters for the first time to cast mail-in ballots, and the return rate is expected to be huge.

Voting rights advocates and some local election officials are worried about a chaotic day as fewer than 200 polling places will be open, down from 3,700 in a typical election year.

The primary will also provide the first test of how significantly the events of the last several weeks will influence electoral politics. Public opinion around police bias has shifted dramatically with more Americans viewing the deaths of black men at the hands of white officers as a broader issue to be addressed.

“I think a lot of people across the country are getting inspired to know that even if you come from the poorest Zip code in one of the poorest states — and, you know, I’m not blind to the fact that I’m a young black man running for U.S. Senate in Kentucky that has never elected someone that looks like me to federal office — that even me, even us, even regular folks, can stand up and lead, and I think that’s the powerful part about all this,” Booker said.

Booker has hit McGrath on showing up too late to a galvanizing moment — she attended her first protest just a week ago. He’s airing a television ad that shows McGrath at a debate this month stumbling to explain why she had yet to join the protesters in Louisville.

McGrath’s campaign said she was unavailable for an interview.

Matt Jones, a Kentucky sports radio host who considered running in the Democratic primary, is backing Booker.

“I would be honest with you — I don’t know anyone that’s voting for Amy McGrath,” Jones said in an interview. “I’m sure they exist, but all the momentum and certainly the sort of excitement is on Booker’s side.

“I think for the longest time, I don’t think Kentuckians were really thrilled with McGrath as the handpicked candidate. I think they sort of felt like she kind of got forced upon them,” he said.

McGrath ran for Congress in 2018 against Rep. Garland “Andy” Barr (R), losing by three percentage points. But national Democrats were impressed with her résumé and how competitive she made that race. The Democratic Senatorial Campaign Committee recruited her to run. Even if beating McConnell was unlikely, the challenge would force McConnell and Republicans to spend resources they could otherwise invest in their more vulnerable candidates.

Despite Booker’s ascent, McConnell’s campaign is treating McGrath like she’ll be its opponent in the fall, even airing an attack ad that describes her as a “radical liberal.”

Senate Minority Leader Charles E. Schumer (D-N.Y.) said this past week, “Amy McGrath is our candidate, she’s a strong candidate.”

David Weigel contributed to this report.