WASHINGTON ― If President Donald Trump wants to make a good first impression with Russian leader Vladimir Putin when they meet Friday, two words he might consider starting with are “thank” and “you.”

Without Putin’s decision to interfere in last year’s presidential campaign on Trump’s behalf, there’s a good possibility he would not have won, given how few votes swung the outcome in the three critical Rust Belt states of Wisconsin, Michigan and Pennsylvania.

Video shows Pres. Trump, Russian Pres. Putin shaking hands at G-20 summit ahead of their high-stakes meeting today. https://t.co/xxeBvDKdjR pic.twitter.com/QunvkPdEFd — ABC News (@ABC) July 7, 2017

Rick Wilson, a Republican political consultant and frequent Trump critic, said the Russian assistance likely swayed 2-to-3 percentage points in those states that proved crucial to the election’s outcome.

“It certainly kept the national Republican base in Trump’s camp,” Wilson said. “Yeah, he should say thank you to Putin. I think this is Donald Trump going to the home office for his quarterly review.”

Tim Malloy, an assistant director of polling for Connecticut’s Quinnipiac University, shied away from ascribing a hard number to the Russia effect ― like most in his profession. But he said the impact’s existence was undeniable.

“There was a blizzard of negativity thrust at [Democratic nominee] Hillary Clinton. With that intense a blizzard, it follows that some of the snow is going to stick,” he said.

Jonathan Ernst / Reuters President Donald Trump speaks by phone with Russia's President Vladimir Putin from the Oval Office on Jan. 28. He is joined by (left to right) Chief of Staff Reince Priebus, Vice President Mike Pence, senior adviser Steve Bannon, press secretary Sean Spicer and then-national security adviser Michael Flynn.

Trump himself, many Republicans and even some Democrats dispute that the meddling was determinative, arguing there is no indication that actual votes were altered by Russian-sponsored hackers.

“Intelligence stated very strongly there was absolutely no evidence that hacking affected the election results. Voting machines not touched!,” Trump tweeted on Jan. 7, the day after U.S. intelligence agencies stated that Russia had interfered in the campaign, and had done so on Trump’s behalf.

Trump’s narrow claim, though, ignores the benefit he received both from hackers as well as an army of pro-Trump bloggers working out of Russia and eastern Europe.

The hackers, according to U.S. intelligence agencies, stole emails from the Democratic National Committee and from Clinton campaign chairman John Podesta, then released politically damaging ones in the campaign’s final weeks. The bloggers wrote and frequently posted false articles about Clinton on Facebook and other social media ― accusing her of corruption, even murder ― in the hopes of flipping her “soft” supporters to Trump or dissuading them from voting at all.

Weird how that happens. What a remarkable coincidence. There was always something there the same day from Russia with love to bail him out. Republican consultant Rick Wilson

Virginia Sen. Mark Warner, the ranking Democrat on the Senate Intelligence Committee, told reporters in March: “There were upwards of 1,000 paid internet trolls working out of a facility in Russia.”

His committee, the House Intelligence Committee and the FBI are all investigating Russian involvement in the election and possible collusion with the Trump campaign.

In a June interview with CNN, Warner said “a lot of smoke” on these matters was worth investigating. “It does seem strange, it appears, that Russian-paid internet trolls who created bots were then able to put forward fake news, selective stories in a way that seemed targeted,” he said.

In early October, shortly after The Washington Post published a story about an “Access Hollywood” tape featuring Trump bragging that his celebrityhood allowed him to grab women by the genitals, the WikiLeaks group released the first of its emails stolen from Podesta’s account.

“Weird how that happens. What a remarkable coincidence,” GOP consultant Wilson said. “There was always something there the same day from Russia with love to bail him out.”

Few political observers disagree that Clinton was a weak candidate, or that her campaign didn’t, in retrospect, make serious strategic mistakes. For example, she and her staff appeared to take Michigan and Wisconsin for granted, failing to make large voter outreach and turnout investments in them.

“The Clinton campaign’s hubris may have contributed more to her defeat than any action the Russians took in this election,” said Neil Newhouse, a Republican pollster with the firm Public Opinion Strategies. “The fact that she represented ‘more of the same’ in a change environment, the campaign’s decision to essentially ignore key states and the inability to communicate a coherent economic message to middle-class voters are all at the root of her loss.”

Still, her losing margins in Michigan, Wisconsin and Pennsylvania were less than a percentage point – a total of about 78,000 votes in all three. Had she won those states, she would be president. Thus, every element in Trump’s favor was by definition a determinative factor ― be it Russian meddling or the announcements by then-FBI director James Comey that he was re-opening, and then re-closing, his investigation into Clinton’s use of a private email server during her tenure as secretary of state.

“In the closely contested races, it was apparently just enough,” said Quinnipiac’s Malloy.

We assess Russian President Vladimir Putin ordered an influence campaign in 2016 aimed at the U.S. presidential election. Russia’s goals were to undermine public faith in the U.S. democratic process, denigrate Secretary Clinton, and harm her electability and potential presidency. Office of National Intelligence report, issued Jan. 6

Trump as of Thursday morning was still disputing Russia’s role in the U.S. election. At a news conference in Warsaw, Poland, he claimed: “I think it could very well have been Russia but I think it could well have been other countries.” He then added: “Nobody really knows for sure.”

That view goes against the consensus analysis of the major U.S. intelligence agencies. The Office of National Intelligence released a report on Jan. 6 stating that Russia not only meddled in the presidential campaign, but specifically wanted Trump to defeat Clinton.

“We assess Russian President Vladimir Putin ordered an influence campaign in 2016 aimed at the U.S. presidential election. Russia’s goals were to undermine public faith in the U.S. democratic process, denigrate Secretary Clinton, and harm her electability and potential presidency. We further assess Putin and the Russian government developed a clear preference for President-elect Trump,” the report said. “We have high confidence in these judgments.”

During his 17-month presidential campaign, Trump frequently praised Putin as a strong leader, even calling him a better one than then-President Barack Obama. When MSNBC’s Joe Scarborough pointed out that Putin has reportedly had political opponents and journalists murdered, Trump answered: “I think that our country does plenty of killing, too, Joe.”

Trump’s Friday meeting with Putin will be his first as president and possibly his first ever, although that is unclear because of Trump’s conflicting statements in the past.

In October 2013, Trump told late night host David Letterman that Putin was a “tough guy” and that he had “met him once.”

In February 2014, Trump told Fox News that Putin had contacted him during his visit to Russia for his beauty pageant.

In October 2015, he told talk radio host Michael Savage that he’d met Putin “a long time ago.”

But at a July 2016 news conference, Trump said he had never met the Russian leader. “I never met Putin,” he said. “I don’t know who Putin is. He said one nice thing about me. He said I’m a genius. I said thank you very much to the newspaper and that was the end of it. I never met Putin.”

Wilson said Trump’s continued kind words for the Russian strongman will come back to haunt Republicans, eventually. “Guys on my side just don’t care,” he said. “If we want to make GOP stand for the ‘Guys Of Putin,’ we’re well on our way.”