Democratic presidential candidate Julian Castro is taking aim at fellow Dems in the House of Representatives for voting against a resolution to introduce articles of impeachment against Republican President Trump.

Castro, who in April became the first Democratic White House contender to call for Trump’s impeachment, told Fox News “I can understand the concerns of some Democrats who have chosen not to support that, but I believe it’s a mistake not to go forward.”

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The former San Antonio, Texas, mayor, who later served as Housing and Urban Development secretary under President Barack Obama, was interviewed a day after the House voted 332-95 to table an impeachment resolution introduced by Rep. Al Green of Texas.

One hundred and thirty-seven Democrats joined all 94 Republicans present in shooting down the resolution. Among the Dems supporting the measure was Castro’s brother, Rep. Joaquin Castro of Texas.

The drive for impeachment over several months has been steadfastly opposed by House Speaker Nancy Pelosi of California and other top Democrats, who worried that it would force vulnerable swing-district lawmakers into peril ahead of next year’s congressional elections.

But Castro disagreed.

“I believe it’s a mistake both substantively and politically,” he argued. “Substantively his actions absolutely merit impeachment proceedings.”

And he warned that “politically they’re risking giving him a clean bill of political health because he’s going to turn around in the fall of 2020 and say, ‘See, they didn’t impeach me because I didn’t do anything wrong.’"

Castro, the only Latino candidate running for president, has made the issue of illegal immigration one of the centerpieces of his campaign. And he has heavily criticized the Trump administration’s handling of illegal migrants at detention facilities.

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In recent weeks there’s been a string of demonstrations outside Immigration and Customs Enforcement (ICE) facilities, during which protesters called for the dissolution of ICE and an end to the crowded detention centers along the southern border.

Even though he supports the demonstrations, Castro said any violent outbreaks during such protests “absolutely” need to stop. “I condemn all violence, and my hope is everybody will make their voice heard in a way that is peaceful and productive."

The Republican National Committee criticized Castro for holding "extreme" positions on immigration.

"Julian Castro continues to ignore the crisis on the Southern border as he calls for the removal of border walls, supports sanctuary cities, and advocates for the decriminalization of illegal immigration," RNC spokesperson Nina McLaughlin said.

Casro, asked in his interview about campaign, said he’s capitalizing on a bump in fundraising to beef up staff at his headquarters and in the early-voting primary and caucus states.

The candidate gave his White House bid a big boost with what many pundits called a breakout performance during the first round of Democratic nomination debates last month.

Castro brought in $2.8 million in the April-June second quarter, nearly triple the $1.1 million he raised in the first three months. Nearly half of his second-quarter haul came in the four days after his June 26 debate performance.

Castro is also getting ready for the second round of debates, which will be held later this month in Detroit. He sees the showdowns – they've watched by millions of Americans – as an opportunity to increase his visibility among voters: “I’m going to keep introducing myself to the American people. My name ID got a lot better after the first debate, but I still have some work to do. So I’m going to keep articulating a positive vision for America’s future and I’m confident that people are going to respond."

Fox News’ Andrew O’Reilly contributed to this report