Many national Democratic leaders think their best shot at defeating Sen. John Cornyn (R-Tex.) is MJ Hegar — a 44-year-old barrier-breaking combat veteran, former Republican and working mom of two young kids who fits the mold of the party’s candidates who flipped Republican-held seats during the 2018 midterm elections.

But a surging pandemic that has killed more than 3,000 Texans, many of them black and Latino, and ongoing protests against systemic racism have given another Democratic candidate a burst of momentum. Royce West, a 67-year-old African American state senator, has held office since Hegar was a teenager and has a long civil rights record, including working with Republicans to pass legislation encouraging the use of body cameras in Texas police departments.

Ahead of Tuesday’s Senate primary runoff between the two, West has cast Hegar as part of the racist system he’s trying to change, while she has cast him as part of the corrupt political system she’s trying to change. The matchup crystallizes a central dilemma for Democrats: Will what worked in 2018 still work in 2020, or does the model need to shift?

“You have one group that has, in many ways, sort of woken up and . . . now places greater importance on having African American elected officials in office,” said Mark P. Jones, a political science professor at Rice University. “This is the way for them to signal that they’re truly progressive and they’re truly concerned about racial justice.”

Yet that does not necessarily mean that many conservatives or independents, who will be the key to beating Cornyn, are also shifting their political preferences, he said.

“One error the media and some observers are making is interpreting silence as support, as opposed to interpreting silence as not wanting to get into it,” he said.

The question of which candidate offers Democrats the better chance in November has taken on fresh importance now that Cornyn, the Senate’s second-ranking Republican, who has had a large advantage in early polls, has made high-profile comments that have angered and energized many Texans. He asked during a Senate Judiciary Committee hearing on police reform in June if systemic racism actually exists; last week, defying medical experts, he defended reopening schools by saying, “We still don’t know whether children can get it and transmit it to others.”

Perhaps signaling his perception of vulnerability, Cornyn’s campaign has started running a TV ad attacking West, labeling him a liberal and comparing him to Sen. Bernie Sanders (I-Vt.) and Rep. Sheila Jackson Lee (D-Tex.), despite his centrist record.

Hegar’s team says Cornyn is trying to draw votes toward West in the runoff because he would be an easier candidate to beat in the fall. The thinking of many Texas political strategists is that in a general election, it would be more difficult for Cornyn to attack a female veteran with no legislative record than a longtime male lawmaker with decades in office.

The choice comes amid renewed optimism by Texas Democrats that the state’s changing demographics and the turn by some key voter groups against Trump have given an opening to presidential candidate Joe Biden as well as the Democratic Senate nominee.

Two years ago, Democrats flipped two suburban congressional districts and picked up 12 seats in the Texas House. Beto O’Rourke, a Democrat and former congressman from El Paso, came close to beating Sen. Ted Cruz (R-Tex.). O’Rourke’s candidacy was boosted by a viral video of his passionate defense of professional football players who kneel in protest of police brutality and racism.

But O’Rourke decided against challenging Cornyn, who is not as loathed by liberals as Cruz is.

With few policy differences between Hegar and West, identity has played a central role in the contest. Hegar, who narrowly lost a House race in 2018, was the first major candidate to get into the race. Some liberals were alarmed that her announcement video contained few if any identifiable people of color, given that nearly 40 percent of Texans are Hispanic or Latino and 13 percent are black. Others felt that her policy stances were too moderate. Soon, 11 other Democrats joined the race, including West, a black city councilwoman from Houston and two Latina activists — all of whom were angered when the Democratic Senatorial Campaign Committee endorsed Hegar in December.

Hegar finished first in the crowded March 3 primary with 22 percent of the vote, less than half the share she needed to win outright. West, who came in second with 15 percent, has been endorsed by five candidates who finished behind him.

West — who has raised about a third as much money as Hegar and has a smaller campaign operation — saw a burst of donations and new volunteers in mid-May when Cornyn’s campaign nicknamed him “Restful Royce,” an insult that West and his allies called racist. He saw a larger influx a few weeks later amid protests following the death of George Floyd, who grew up in Houston, at the hands of police in Minneapolis. And his campaign was boosted again in late June after he and Hegar tensely sparred over whose experience was more needed in Washington.

In the final minutes of that debate, the two candidates were prompted to ask each other a question. Hegar asked West to name some things that unite them, while West asked Hegar why she made a small campaign donation to Cornyn in 2011, at a time when “the tea party was giving President Obama hell.” Hegar scolded him for asking an “intentionally misleading” question and said she had to make the donation to get a meeting to advocate for policy changes.

“It’s a broken system. It’s a system you’re a part of, by the way, and that you’ve been upholding,” she said. “We have corruption, we have money in politics, we have politicians — frankly, like you, Royce — who have become millionaires in office.”

“I’m from the projects of Dallas,” West retorted. “If you’re going to take a shot at me because I am a successful lawyer, basically providing job opportunities for people in my community, then take that shot. I have no problems with that.”

West has long faced questions about the millions of dollars in legal fees that his law firm has collected over the years by representing government entities. While this is legal in Texas — and many state lawmakers have done it — Democratic strategists say it could be seen as unethical by some voters and would probably be seized upon by Cornyn in a general election.

West said in an interview that he is “very, very careful in making certain that there is no conflict” when he accepts work, adding that last year he was named “legislator of the year” by an association of state, county and district attorneys, something he said wouldn’t have happened “if I had an ethics problem.”

West’s team has cast this line of attack as a racist one. A spokesman sent an email to the Austin American-Statesman newspaper comparing Hegar’s comments to those of older whites seeing a black man driving a nice car and wondering how he could afford it. In an email to supporters last week, West wrote: “So many people are conditioned to question the achievements of a minority person. We as a nation are waking up to systemic racism and the filters or screens it creates through which we see others. I think Hegar’s screen needs a little cleaning.”

Hegar considers his rejoinder unfair and divisive. Although she grew up in a mostly white, conservative town outside Austin, she said that she thrived in the Air Force’s “melting pot of races, genders, cultures, religion, just everything.”

“I’m always the first person to criticize myself and to look at something again,” Hegar said in an interview when asked to respond to West’s criticism. “He mistook what I said for, ‘You can’t be a successful businessman.’ I’m talking about ethics. I’m talking about corruption.”

Since the coronavirus began to spread in Texas soon after the March primary, Hegar has continued to call for changes to the U.S. health-care system and has highlighted the racial and economic disparities exacerbated by the crisis. As she virtually campaigns from home, her 5-year-old’s toys and artwork are often prominently displayed behind her.

Amid the protests sparked by Floyd’s death, Hegar’s team decided that her voice should not be the dominant one on issues of race. She has instead tried to elevate blacks and Latinos, especially women, including relatives of Javier Ambler II, who died last year after being tased multiple times by police in Austin.

“We’re wanting his story to be heard. Most importantly, we’re wanting change,” his sister Kim Ambler said in a video posted on Hegar’s Facebook page.

Hegar’s team argues that she has done more to directly engage Latino voters than has West, who said he is relying on black and Latino state lawmakers, unions and advocacy groups that have endorsed him to help him turn out voters.

At the end of their debate in late June, each candidate had two minutes to make a final pitch to voters.

“Royce West has been in the mix getting things done,” the state senator said of himself. “And so if you want someone who is inexperienced, I understand that, but the question is: Does experience really matter?”

“Experience does matter,” Hegar said in her closing, “and I don’t know about you, but I’m tired of career politicians condescending to me that my 12 years in uniform — bleeding for our Constitution on foreign soil — five years working in health care or my experience as a mom of a 3- and 5-year-old are not important enough to consider.”