Julian Castro, the grandson of a Mexican immigrant who became San Antonio mayor and a U.S. housing secretary, suspended his 2020 Democratic presidential run on Thursday after a candidacy overshadowed by more famous liberals. 

The departure of the only Latino from the campaign, a month or so ahead of early nominating contests in Iowa and New Hampshire, leaves 14 Democratic candidates in a still crowded field seeking the party's nomination to take on Republican President Donald Trump in November. 

The charisma and assertiveness that helped make Castro, 45, a rising star in the Democratic Party did not translate into enough support to compete against better-known candidates, including progressive U.S. Senators Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts. 

He had struggled to raise money for what was seen as a long-shot bid, and another Texan who was seeking the party's nomination before dropping out in November, former U.S. Representative Beto O'Rourke, siphoned some attention from Castro in the early days of his campaign. 

"It's with profound gratitude to all of our supporters that I suspend my campaign for president today," Castro wrote in a Twitter post. 

"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 said in a video released by his campaign. 

Castro championed immigrant rights and was a strong critic of Trump and his policies. 

He did not flinch from criticizing his fellow Democrats either, notably going after former U.S. Vice President Joe Biden, the early front-runner among Democrats, during a September 12 debate. 

However, other Democratic candidates posted gracious messages for Castro on Twitter after he announced his withdrawal from the race. Among them, Biden said Castro had led his campaign with "grace and heart," while Sanders praised him for his "fight for a humane immigration system" and Warren thanked him for being a "powerful voice."

Castro's departure could intensify criticism that, for a party that prides itself on its diversity, most of the top Democratic candidates are white. Asian-American Andrew Yang was the only minority candidate to appear beside six others in the most recent debate on December 19. 

The race for the party's presidential nomination remains up for grabs just weeks before the first votes are cast in Iowa on February 3, with the New Hampshire primary to follow on February 11. 

There is a three-way battle at the top of national opinion polls among Biden, Sanders and Warren, and South Bend, Indiana's former mayor, Pete Buttigieg, has risen to lead some polls in early voting states.