AUSTIN, Texas (AP) — Former Obama housing secretary Julián Castro, the only Latino in the 2020 Democratic presidential primary race, ended his campaign Thursday after a yearlong run in which he pushed his rivals on immigration and took big swings in debates but struggled to break through with voters.

“I’m so proud of the campaign we’ve run together. We’ve shaped the conversation on so many important issues in this race, stood up for the most vulnerable people and given a voice to those who are often forgotten,” Castro said in a video announcing his exit. “But with only a month until the Iowa caucuses, and given the circumstances of this campaign season, I have determined that it simply isn’t our time.”

Castro, who launched his campaign last January, dropped out after failing to garner enough support in the polls or donations to qualify for recent Democratic debates. A former San Antonio mayor who later became President Barack Obama’s secretary of Housing and Urban Development, Castro had stalled for most of his campaign, hovering around 1% in polls, and never came close to raising money like his better-known challengers.

He had not yet released his end-of-year fundraising numbers, but by October had raised less than $8 million total. As Castro exited the field, Bernie Sanders announced on Thursday that he brought in more than $34.5 million in the previous three months alone.

Castro’s departure reflects the increasing lack of color in a Democratic field that began as one of the most diverse in history. Between Sen. Kamala Harris of California dropping out and Sen. Cory Booker of New Jersey also lagging, the sixth and final Democratic debate of 2019 had no black or Latino candidates onstage.

Last month, Castro said women and candidates of color were being pushed aside in the race because of what he called “the media’s flawed formula for ‘electability.’” He also ran an ad in majority-white Iowa, arguing that the state should no longer vote first in Democrats’ nominating process because it doesn’t reflect the diversity of the party.

“There is a strategic disadvantage when you don’t have a very diverse population or electoral base in those states,” said Jeronimo Cortina, a political science professor and associate director of the Center for Mexican American Studies at the University of Houston. “You can see that minority candidates have a harder time to run in these primary election seasons.”

Castro, 45, was among the youngest in the running at a moment when the party’s ascendant left wing is demanding generational change. And as the grandson of a Mexican immigrant, Castro said he recognized the meaning of his candidacy in the face of President Donald Trump’s inflammatory anti-immigrant rhetoric and hard-line policies on the U.S.-Mexico border.

But he labored not to be pigeonholed as a single-issue candidate. He made Puerto Rico his first campaign stop, recited the names of black victims killed in high-profile police shootings and was the first in the field to call for Trump’s impeachment. He also was a leading voice in the field on poverty and ending hunger.

But his sagging poll numbers never budged. Early on, he was often eclipsed by another Texan in the race who dropped out this fall, former Rep. Beto O’Rourke, and another young former mayor, Pete Buttigieg of South Bend, Indiana. His campaign and supporters, meanwhile, grumbled that he didn’t get due credit for taking out-front positions.

Castro’s former challengers said his voice would be missed.

“Secretary Castro brought a firm, clear, moral voice to this primary,” Elizabeth Warren said during a campaign stop in New Hampshire. “I’m very sorry that he’s not part of this, but I know he has an important voice in American politics and that we’re going to hear a lot more from him both in 2020 and in years to come.”

Trying to show he could go toe-to-toe with Trump, Castro swung for big moments on debate stages, and he flirted with a much-needed breakout in June after confronting O’Rourke over not supporting decriminalization of illegal border crossings.

But turning his sights on Joe Biden on a later stage brought swift backlash. During the September debate in Houston, Castro appeared to touch on concerns about Biden’s advancing age and added a parting shot at the then-76-year-old former vice president.

“I’m fulfilling the legacy of Barack Obama, and you’re not,” Castro said.

Castro denied taking a personal dig at Biden as others in the field condemned the exchange. Three days later, Castro lost one of his three backers in Congress, Rep. Vicente González of Texas, who switched his endorsement to Biden.

In October, Castro had warned supporters in a fundraising appeal that failing to make the November debate stage would spell the end of his campaign. He needed to hit at least 3% polling in four early state or national polls but didn’t get even one.

What is next for Castro is unclear. Back home in Texas, Democrats had long viewed Castro as their biggest star in waiting, and some have urged him to run for governor as the state trends more diverse and liberal.

Castro was pegged as a rising Democratic star after being elected as mayor of the nation’s seventh-largest city at age 34, and he was on the short list for Hillary Clinton’s running mate in 2016.

In the video announcing his exit, Castro concludes with “¡Ganaremos un día!” — which translates to “We will win one day!”