Shortly after blasting President Trump's immigration policies as a "form of torture," a top Democratic congressman collapsed from what a spokesperson described as heat exhaustion at a rally near the White House.

Rep. Joe Crowley, D-N.Y., 56, who chairs the House Democratic Caucus, tweeted Wednesday afternoon that his condition had stabilized. "Thanks for everyone's concern -doing fine now," he wrote. "Wish I could say the same for the children and parents at the border."

Fox News has confirmed that Crowley was taken to a hospital, is responsive and should be OK. But details about the episode remain unclear.

Crowley has been well-positioned to move up in the House Democratic leadership, currently headed by minority leader Nancy Pelosi and minority whip Steny Hoyer -- both of whom are 78 years old.

The House Democratic Caucus, which Crowley chairs, is enormously influential and plays a key role in selecting Democratic House leadership and forming party policy.

Video from the rally in Washington, where temperatures soared to over 85 degrees with high humidity on Wednesday, showed bystanders encircling Crowley and offering him water.

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Crowley has been a vocal opponent of the Trump administration's immigration policies, and earlier on Wednesday he took aim at Republicans who espouse "family values" but impose "psychological torture" on illegal immigrants.

The New York Democrat specifically cited reports that illegal immigrant children are increasingly being separated from their parents because of the White House's new "zero-tolerance" policy, which ramps up prosecutions of those attempting to enter the country unlawfully.

Crowley also criticized Attorney General Jeff Sessions for a ruling this week that will limit the ability of domestic violence and gang violence victims to seek asylum in the U.S.

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Sessions said he made the change because asylum law had been stretched too far to allow those claims to form the basis for an asylum application. He also insisted that many of the claims were fraudulent, and that the asylum system has been overburdened by all the applicants.

"The vast majority of the current asylum claims are not valid," Sessions said in remarks on Monday. "For the last five years, only 20 percent of claims have been found to be meritorious after a hearing before an immigration judge."

Fox News' Chad Pergram contributed to this report.