Political observers and politicians from both major U.S. parties reacted with disgust to Monday’s press conference between U.S. President Donald Trump and Russian President Vladimir Putin in Helsinki, during which Trump openly questioned his own administration’s conclusion that Russia tried to undermine the 2016 U.S. presidential election.

"I don't see any reason why Russia would interfere in the 2016 election," Trump told astonished reporters.

University of Mary Washington professor Steve Farnsworth called the comments a “big win for Vladimir Putin,” considering that 12 Russians were indicted on Friday for interfering in the 2016 U.S. election.

Farnsworth said the meeting should never have happened in the first place, likening it to U.S. President Franklin Delano Roosevelt meeting with Japan’s Emperor Hirohito after the 1941 attack on Pearl Harbor.

“You are rewarding a dictatorship that’s occupying other countries in Europe, that has done more than almost any country in the world to manipulate the American electoral process,” Farnsworth told CTV News Channel.

Farnsworth said that America fought the Cold War with Soviet Russia based on the idea that America’s positon in the world is “enhanced by the promotion of free societies and democratic societies.”

“It is really astonishing that that huge advantage that America has had -- an advantage that has been used by Republican and Democratic presidents (alike) in the fighting against authoritarianism for 80 years -- is simply walked away from by President Trump,” Farnsworth added.

Republican strategist Cory Crowley said that Trump showed “disgusting” weakness and pointed out that Trump had frequently criticized his predecessor, Barack Obama, for his perceived weakness on the global stage.

However, Crowley said the Democrats will have trouble convincing the American public of just how damaging the press conference was, because “neither party and very few people in Washington have any credibility” on foreign policy. In his view, Obama failed to project U.S. strength abroad.

“If the Republicans remain quiet, there’s going to be nobody left with integrity,” Crowley said.

Crowley added that Republican Sen. John McCain is “one of very few people who can speak with credibility in this situation.”

McCain: Trump ‘abased’ himself before a ‘tyrant’

McCain, who lost to Obama in 2008, called the press conference “one of the most disgraceful performances by an American president in memory.”

“President Trump proved not only unable, but unwilling to stand up to Putin,” McCain said in a statement Monday afternoon. “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.”

“No prior president has ever abased himself more abjectly before a tyrant,” McCain went on.

“Not only did President Trump fail to speak the truth about an adversary; but speaking for America to the world, our president failed to defend all that makes us who we are—a republic of free people dedicated to the cause of liberty at home and abroad,” he added.

Former Florida governor Jeb Bush retweeted McCain’s statement, as did Democratic New York Sen. Chuck Schumer.

Schumer: ‘Thoughtless, dangerous, and weak.’

Schumer stated on Twitter that “In the entire history of our country, Americans have never seen a president of the United States support an American adversary the way (Trump) has supported President Putin.” He called Trump’s actions “thoughtless, dangerous, and weak.”

Meanwhile, top Republican Paul Ryan, Speaker of the House of Representatives, said in a statement that there is “no question that Russia interfered in our election and continues to undermine our democracy.”

“The president must appreciate that Russia is not our ally,” the Wisconsin Congressman went on. “There is no moral equivalence between the United States and Russia, which remains hostile to our most basic values.”

Sen. Flake: ‘This is shameful’

Arizona Republican Sen. Jeff Flake, a frequent critic of Trump who has said he will not seek re-election, called the press conference “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,” Flake tweeted.

Sen. Corker: ‘Good day for Putin’

Sen. Bob Corker of Tennessee, chairman of the Senate Foreign Relations Committee, called it a “very good day for President Putin."

Corker said Trump seems to care more “about how a leader treats him personally” than pushing back against meddling in the election.

Paul: ‘Trump derangement syndrome’

Republican Sen. Rand Paul seemed to defend Trump’s approach to Russia.

The Kentucky senator told The Associated Press that he believes it's important for the U.S. to keep an open dialogue with its adversaries.

Paul also said that lawmakers and former intelligence officials criticizing the U.S. president are experiencing "Trump derangement syndrome."

Coats: ‘We have been clear’

Dan Coats, the United States Director of National Intelligence, issued a statement saying the intelligence community provides “fact-based assessments” to the president.

“We have been clear in our assessments of Russian meddling in the 2016 election and their ongoing, pervasive efforts to undermine our democracy, and we will continue to provide unvarnished and objective intelligence in support of our national security,” Coats added.

Pelosi: ‘What do the Russians have on Trump?’

Democratic Leader of the House of Representatives Nancy Pelosi said on Twitter that she finds herself asking, “what do the Russians have on (Trump) personally, financially, & politically?”

“The answer to that question is that only thing that explains his behavior & his refusal to stand up to Putin,” she added.

Sanders: ‘Pathetic performance”

Vermont Sen. Bernie Sanders wrote on Twitter: “Millions of Americans have risked their lives to defend our democracy. What would those brave men and women think if they saw President Trump's pathetic performance today?”

Harris: “Disgraceful”

Calfornia Sen. Kamala Harris wrote on Twitter: “Trump flattered Putin who attacked our democracy and insulted the brave men and women of our Intelligence Community. It is disgraceful.”

With files from The Associated Press