Why is a Republican former mayor of Los Angeles endorsing Democrat Loretta Sanchez for the open Senate seat in California?

Because “she is tough and not afraid to take a stand on important issues,” Richard Riordan, who is credited with helping the city recover and rebuild after the deadly 1992 riots, said in a recent statement released by Sanchez’s campaign.

Also because there will be no Republican candidate on the ballot in November for the Senate seat being vacated by the retiring Barbara Boxer (D-Calif.).

If Sanchez, a 10-term congresswoman from Orange County, wants to boost her chances of winning in November, she will probably have to do so by forming an unusual coalition of Latinos and Republicans. That could be challenging in a year when Donald Trump, whose derogatory comments toward Latinos are widely known, will be at the top of the ballot.

Bill Carrick, Sanchez’s chief strategist, said his candidate will not change her “values or ideology” in an effort to appeal to Republican voters. “It would be ridiculous for her to all of a sudden start sounding like a Republican,” he said. “That’s not going to happen.”

Under the state’s primary system, the top two vote-getters advance to the general election, even if they are members of the same party. Sanchez placed second in the June 7 primary. The top vote-getter was California Attorney General Kamala Harris, who led Sanchez by more than 20 percentage points.

But GOP voters, some of whom view Harris as another San Francisco liberal, might feel more comfortable with Sanchez, Carrick said. “She comes from Orange County, and overall the county is Republican,” he said. “People know she’s worked at the local level to get things done.”

Republicans make up 27 percent of California voters. In a Field Poll survey a week before the primary, Republicans were split when asked which Democrat they would vote for in November — 26 percent Harris and 25 percent said Sanchez. Thirty percent of GOP voters volunteered that they would vote for neither. The poll showed Harris leading Sanchez 40 percent to 26 percent overall in a general-election contest.

Both women are aiming to make history and are attracting national attention: Harris, who is Asian American and black, could become the only African American female senator. Sanchez, who is the daughter of Mexican immigrants, could be one of the first Latinas in the Senate. (Another Latina, Catherine Cortez Masto, is running for the retiring Harry Reid’s Senate seat in Nevada).

Sanchez, 56, is seen as something of the underdog, fighting to mobilize the state’s Latino population after upsetting then-Rep. Bob Dornan (R-Calif.) in 1996 in a vastly changing district.

She starts the general election with less name recognition and organizational support than her opponent, who has won two statewide contests. Sanchez has the support of the Congressional Hispanic Caucus’s BOLD PAC and some California labor groups, but she will not have the organizational support of a major political party or the state’s big labor unions. Harris has the backing of the California Democratic Party and labor giants such as the Service Employees International Union.

Sanchez also has struggled to raise money. According to campaign finance reports filed three weeks before the primary, Sanchez had $1.3 million on hand out of $3.5 million raised during the past year. Harris had $4.7 million left over from $11 million raised for the primary.

“Fundraising was a challenge, and we have to double down and work harder and do a better job in California and outside of California raising money,” Carrick said.

On the campaign trail, Sanchez describes herself as a Blue Dog Democrat and touts her assignments on the House Armed Services and Homeland Security committees. She tells voters she already knows how Congress works and would be more prepared than her opponent to have influence in the Senate.

But Carrick also pointed out that Sanchez is clearly left of center on certain issues such as abortion rights and that “many things about her are progressive.”

Sanchez also supported the Affordable Care Act and Obama’s executive order shielding certain young immigrants and their parents from deportation, policies generally not favored by Republicans.

Carrick said it is not unusual for voters to cross party lines in state races. He noted that Riordan has endorsed Democrats in the past, including then-candidate Barack Obama in 2008 and Sen. Dianne Feinstein (D-Calif.).

“Loretta knows how to work with Democrats, Republicans, and Independents. She is the leader we need in the U.S. Senate,” Riordan said last week in his endorsement statement.

Sanchez might find an opening with independents, who make up 23 percent of registered voters in the Golden State. While the Field Poll showed them favoring Harris 40  to 26 percent in a general election, 28 percent said they were undecided.

In an interview with the Los Angeles Times, Riordan cited a program that Harris created while she was the San Francisco district attorney that allowed a convicted drug dealer to avoid prison time. The man later committed another crime. “I think she’s a crazy liberal,” Riordan said.

Harris, 51, was first elected attorney general in 2010, in a photo-finish race against a Republican district attorney from Los Angeles. She was easily reelected in 2014 and has been the favorite to win the Senate seat since announcing her candidacy 18 months ago. She has the backing of Gov. Jerry Brown (D), dozens of Democratic state lawmakers and local officials, and such national party VIPs as Sen. Elizabeth Warren (D-Mass.).

Her campaign points to her performance in the primary as evidence that Harris also is popular with voters across party lines. Unofficial results showed Harris took 40 percent of the vote, with Sanchez getting 18.9 percent. A total of 34 candidates were on the primary ballot, and the highest-polling Republican got 8 percent of the vote.

“Kamala Harris won more Republican and independent votes than Congresswoman Sanchez in the primary and is beating her with those same groups, as well as almost every other segment of the electorate, in general election polling,” said Nathan Click, a spokesman for Harris’s campaign.

Harris’s pollster, in a conference call with reporters the day after the primary, questioned the strategy of a winning coalition made up of Latinos and Republicans supporting presumptive GOP nominee Donald Trump.

“In all my years of doing California politics, I’ve never seen a coalition of Republicans and Latinos come together to support a candidate,” David Binder said. “And given this GOP nominee, with his insults toward Mexican Americans, it’s very difficult to see Latinos support candidates supported by Republicans going into November.”

Luis Alvarado, a Republican strategist who also is Hispanic, said he is not supporting Trump, but he plans to vote for Sanchez in the general election.

“Republicans will find Loretta to be the most conservative of the choices and most open to work with Republican leaders in the state,” Alvarado said this week. “Where AG Kamala Harris is seen to be an extension of the liberal movement in San Francisco, Loretta has proven to be an independent thinker who stands by her policy positions independently.”

Kaitlyn MacGregor, spokeswoman for the California Republican Party, said she had “no comment on Republicans who choose to engage” in the Senate race, adding it was not a priority for the state or the national party. No Republican has been elected to statewide office since 2006.

The campaign office for House Majority Leader Kevin McCarthy (R-Calif.) did not respond to a request for comment on the Senate race.

Howard P. “Buck” McKeon, a Republican who left the House last year after more than 20 years representing parts of Los Angeles and Ventura counties, said he had “a great working relationship” with Sanchez.

McKeon chaired the Armed Services Committee. “I’d watch her during votes, and she’d come over and be working our side on some issues,” he said. “She didn’t just come and sit down — she’s moving all the time, so I respect that.”

He said that he hasn’t followed the Senate race closely but that “people have told me her opponent is left of Boxer, and that would be enough for me.”

“If I lived in California, I’d be voting for Loretta,” said McKeon, who now resides in Arlington, Va.