By PAUL J. WEBER
Associated Press

SAN ANTONIO (AP) - Democratic presidential candidate Julián Castro is back in Texas and trying to break out of the back of the pack.

Castro will join many of his 2020 rivals Wednesday at a candidate forum in Houston. That includes former Texas congressman Beto O'Rourke, whose popularity back home has illustrated some of the challenges Castro is facing.

Castro entered the race as a fast-climber in the Democratic Party. He was elected San Antonio mayor at age 34 and was an Obama Cabinet member and a contender for Hillary Clinton's running mate in 2016.

But he lags in polling and fundraising and still hasn't been guaranteed a spot in the first debates this summer.

Bigger name are struggling for a foothold, too, and Castro aides point to a donor uptick in April.

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