The top Democrats on Capitol Hill responded to President Donald Trump siding with Vladimir Putin over his own intelligence agenices by saying more forcefully the Russian president might have compromising information about him.

House Minority Leader Nancy Pelosi, D-Calif., last week suggested Putin might have damaging information about the U.S. businessman-turned-president. On Monday, she went a step further, saying the president’s “weakness” during the Helsinki summit “proves” the Kremlin has something on him.

A short time later, it was Senate Minority Leader Charles E. Schumer’s turn. He told reporters that one big question “hangs” over the Trump presidency: “What could possibly cause President Trump to put the interests of Russia over those of the United States?”

Schumer described himself as “appalled” by Trump’s performance at a joint press conference with Putin during which the U.S. leader refused to state Russia interfered in the 2016 election and contradicted his own intelligence agency bosses.

He called Trump’s performance “thoughtless” and “dangerous” and “weak.”

“The president is putting himself over our country,” Schumer said, adding Trump should have taken the 12 indictments of Russian intelligence officers to the summit and “demanded justice.” Instead, Trump “took the word” of the Russian intelligence community over that of his own, he added.

“The question now looms: What, if anything, will Congress do? … Where are our Republican colleagues?” Schumer said.

If Putin does not have something on Trump, “what the heck could it be?” the New York Democrat said, echoing Pelosi.

GOP members could act immediately to restrain Trump’s foreign policy moves, Schumer said.

He wants them to “ratchet up” sanctions against Russia; “demand” the president’s national security team promptly testify about the behind-the-scenes parts of the week-long European trip; end “once and for all the attacks on the Justice Department, FBI and Special Counsel Robert S. Mueller; and insist “loudly and clearly” that those 12 indicted Russians be sent to the U.S. to stand trial.

On the sanctions piece, Schumer urged the rejection of a proposal that would loosen some penalties on Russia as part of the current defense policy debates at the Capitol.

“In the House there is right now an effort to ratchet these sanctions down. Given what Mr. Putin said today, given the indictments, given what Mr. Trump said today, that cannot happen,” said Schumer.

“As you know, the House Republicans have been pushing a provision in the defense bill that would create a loophole in sanctions targeted at Putin’s defense and intelligence sectors,” he told reporters. “They should drop that immediately.”

Schumer, saying he is “pleading” with GOP leaders to act, also called on Trump to agree to be interviewed by the special counsel.

“The president is doing grave harm to the standing of these United States while kowtowing to … Vladimir Putin,” Schumer said. “The best people to check him are not Democrats, but his fellow Republicans.”