President Trump’s refusal Monday to denounce Russian President Vladimir Putin for interfering in the 2016 U.S. presidential campaign sparked pointed criticism from Republican leaders, including several of Trump’s legislative allies who warned that his actions could ultimately hurt national security interests.

At a joint news conference with Putin in Helsinki, Trump spoke admiringly of Putin’s denials and said he did not “see any reason why” Russia would be at fault for election-year hacking, effectively siding with the Russian leader over the assessment of the U.S. intelligence community.

Within hours of the event’s conclusion, Republicans had joined Democrats in criticizing the president’s comments. Many more in the president’s party reasserted the findings of Russian culpability, distancing themselves from their leader.

“The president must appreciate that Russia is not our ally,” said House Speaker Paul D. Ryan (R-Wis.). “The United States must be focused on holding Russia accountable and putting an end to its vile attacks on democracy.”

Rep. Trey Gowdy (R-S.C.), a Trump ally and a fierce critic of the FBI’s investigation of election meddling, released a statement calling on top administration officials to tell Trump “it is possible to conclude Russia interfered with our election in 2016 without delegitimizing his electoral success.”

Republican senators also were quick in their criticism of Trump’s statements. “Shameful,” tweeted Sen. Jeff Flake (Ariz.). “Bizarre and flat-out wrong,” wrote Sen. Ben Sasse (Neb.) in reference to Trump’s separate assertion that both countries were to blame for their deteriorating relationship. “Missed opportunity,” said Sen. Lindsey O. Graham (S.C.), who added that Trump’s answer “will be seen by Russia as a sign of weakness and create far more problems than it solves.”

Since Trump’s inauguration, members of his party on Capitol Hill have stifled much of their criticism of the president to preserve their own electoral viability and their ability to maintain private channels of communication with him. Trump’s statements on Monday threatened that stance perhaps more than at any time since his defense last summer of Nazi sympathizers in Charlottesville during a dispute over Confederate statues.

At the Capitol on Monday, Senate Majority Leader Mitch McConnell (R-Ky.) declined to respond to a reporter’s questions about whether he was disappointed with Trump’s statements.

“As I have said repeatedly, the Russians are not our friends and I entirely agree with the assessment of our intelligence community,” he said as he walked into the Senate chamber.

Some of the sharpest words Monday came from senators who have focused on foreign policy, a position that has often left them at odds with a president intent on upending traditional U.S. relationships.

Sen. Bob Corker (R-Tenn.) said Trump’s comments made the United States look “like a pushover.”

“I think sometimes he forgets the fact that these intelligence agencies report and work for him,” Corker said. “Time and time again, he makes decisions not based on what’s good for the country but how someone treats him. And that was very evident today.”

In a statement, Sen. John McCain (R), who is being treated for brain cancer in his home state of Arizona, said: “Today’s news conference in Helsinki was one of the most disgraceful performances by an American president in memory. No prior president has ever abased himself more abjectly before a tyrant.”

Russia experts warned that Trump’s refusal to blame Putin for the election interference would fulfill what U.S. prosecutors have described as a central Russian goal of its covert campaign in the United States: to sow domestic discord.

“We are now going to fight amongst ourselves,” said Michael McFaul, who served as ambassador to Russia under President Barack Obama. “We are not going to develop strategies to counter Russia. We are going to be diminished on the playing field.”

Trump has not demonstrated a similar concern, as he has worked to shift his party’s foreign policy focus.

In 2012, Republican presidential nominee Mitt Romney declared Russia the nation’s “Number One geopolitical foe” — a position reflecting decades of Republican orthodoxy that was cheered at the time by conservatives who had criticized Obama for telling a Russian official that he would have “more flexibility” after his reelection.

When CBS News asked him on Saturday to identify the nation’s “biggest foe” right now, Trump pointed to the European Union before mentioning Russia or China. (In a statement Monday, Romney, now running for a Senate seat in Utah, called Trump’s words “disgraceful and detrimental to our democratic principles” and said his behavior “undermines our national integrity and impairs our global credibility.”)

Yet Trump’s stance has tilted public opinion, with Republicans becoming more favorable toward Russia.

A January poll by the Pew Research Center found that 38 percent of Republican-leaning voters viewed Russian power and influence as a major threat to the United States, down from 58 percent in 2015. By contrast, 63 percent of Democratic-leaning voters considered Russia as a major threat in January.

The nation’s intelligence agencies, in a January 2017 assessment, concluded that Russians were responsible for stealing documents that were later released online from the Democratic National Committee and other senior Democratic officials. A federal criminal indictment was filed against a dozen Russians on Friday.

During the presidential campaign, Trump initially blamed the hacking of Democratic accounts on Democrats.

Even after winning the election, Trump refused to accept the view that Russia had targeted the campaign. “I don’t believe it. I don’t believe they interfered,” he said weeks after his victory.

Since then, he has waffled, saying at times that it may have been Russia and at other times that he found Russian denials credible, as he did Monday. “I have great confidence in my intelligence people, but I will tell you that President Putin was extremely strong and powerful in his denial today,” Trump said in Helsinki.

Last week, 97 senators voted for a nonbinding resolution that called for the Trump administration to “counter malign activities of Russia that seek to undermine faith in democratic institutions in the United States and around the world.” Rand Paul (R-Ky.) and Mike Lee (R-Utah) were the only senators to vote against the measure, which also reaffirmed the U.S. commitment to the North Atlantic Treaty Organization. McCain, who was absent, did not vote.

“This is not one of these issues with respect to the intelligence community that is questionable or unsubstantiated,” said Sen. Jack Reed (D-R.I.), who wrote the resolution, noting that the Senate has been thoroughly briefed on the intelligence pointing to Russia’s culpability. “And I have seldom heard any of my colleagues question that conclusion.”

Former House speaker Newt Gingrich (R-Ga.), a Trump ally whose wife serves as U.S. ambassador to the Vatican, wrote on Twitter on Monday afternoon that Trump must clarify his statements about Putin and the U.S. intelligence community.

“It is the most serious mistake of his presidency and must be corrected — immediately,” Gingrich wrote.

Sean Sullivan, Mike DeBonis and Amy B Wang contributed to this report.