HELSINKI (NBC) — President Donald Trump was swiftly rebuked by lawmakers, TV anchors and pundits across the political spectrum Monday after his joint news conference in Finland with Russian President Vladimir Putin.

Sen. John McCain, R-Ariz., who has criticized the president’s posture toward Russia in the past, called it “one of the most disgraceful performances by an American president in memory.”

In a lengthy statement, he called the summit, which took place between the Trump and Putin at Finland’s presidential palace Monday in Helsinki, a “tragic mistake” — and said that dismissing the news conference that followed as a “pathetic rout” of a political novice was too generous.

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“President Trump proved not only unable, but unwilling to stand up to Putin. He and Putin seemed to be speaking from the same script as the president made a conscious choice to defend a tyrant against the fair questions of a free press, and to grant Putin an uncontested platform to spew propaganda and lies to the world,” McCain said.

“No prior president has ever abased himself more abjectly before a tyrant,” he added.

Former CIA director John Brennan, a Democrat and a frequent Trump critic, called Trump’s performance at the news conference “nothing short of treasonous.”

Retiring Sen. Jeff Flake, R-Ariz., called it “shameful.”

“I never thought I would see the day when our American President would stand on the stage with the Russian President and place blame on the United States for Russian aggression. This is shameful,” Flake, another frequent critic of the president, said on Twitter.

At the news conference held after the summit, Trump downplayed the assessment of the U.S. intelligence community that Moscow mounted an effort to help him win the presidency in 2016.

“[Putin] just said it’s not Russia,” Trump said. “I will say this: I don’t see any reason why it would be.”

House Speaker Paul Ryan, R-Wisc., who rarely criticizes Trump publicly, contradicted Trump’s equivocations about Moscow’s election meddling and said “the president must appreciate that Russia is not our ally.”

“There is no question that Russia interfered in our election and continues attempts to undermine democracy here and around the world,” Ryan said in a statement.

“There is no moral equivalence between the United States and Russia, which remains hostile to our most basic values and ideals. The United States must be focused on holding Russia accountable and putting an end to its vile attacks on democracy,” Ryan added.

Standing next to the Russian leader, Trump also bashed the Democratic Party, the FBI, special counsel Robert Mueller’s probe into Russian election meddling, Hillary Clinton and members of the news media.

It was “the most astonishing display of weakness and submission that I have ever seen from an American President,” Rep. Don Beyer, D-Va., said.

“For the President of the United States to stand next to Vladimir Putin — who personally ordered one of the largest state-sponsored cyber-attacks in our history — and side with Putin over America’s military and intelligence leaders is a breach of his duty to defend our country against its adversaries.

“If the President cannot defend the United States and its interests in public, how can we trust him to stand up for our country in private?” 
-U.S. Sen. Mark R. Warner (D-Va.)

This is a sad, shameful moment for our great nation. We will reclaim our values and reassert our global leadership. We’ll turn the page on this dark chapter. But it won’t happen on its own. We all must stand up—to side with U.S. law enforcement and to protect all Americans.
-U.S. Sen. Tim Kane (D-Va.)

“A person can be in favor of improving relations with Russia, in favor of meeting with Putin, and still think something is not right here,” tweeted Rep. Justin Amash, R-Mich.

Abby Huntsman, a Fox News reporter and daughter of U.S. Ambassador to Russia Jon Huntsman, excoriated Trump in a tweet, saying “no negotiation is worth throwing your own people and country under the bus.”

Sen. Lindsay Graham, R-S.C., also called Trump’s remarks a “missed opportunity” to hold Russia accountable.

“This answer by President Trump will be seen by Russia as a sign of weakness and create far more problems than it solves,” Graham said in a tweet.

House Minority Leader Nancy Pelosi, D-Calif., called Trump’s performance an embarrassment and suggested, without evidence, the Russians may have damaging information about the president.

“President Trump’s weakness in front of Putin was embarrassing, and proves that the Russians have something on the President, personally, financially or politically,” she said in a statement.

“This is a sad day for America, and for all Western democracies that Putin continues to target.”

Rep. Eliot Engel, D-N.Y., the ranking member of the House Committee on Foreign Affairs, called the news conference a “disgrace.”

“Because of the President’s reckless and disgusting behavior, the entire week has been a disaster for American leadership and our standing in the world. What will it finally take for my Republican colleagues in Congress to stop covering for this President and stand up for our country?” Engel said in a statement.