A "deep dive" of the 2020 election compiled by House Democrats blames bad polling that underestimated voter turnout by supporters of then-President Trump, as well as effective messaging by House Republicans that focused on the far left’s "defund the police" movement, for the party’s underwhelming performance in congressional elections last November.

The GOP controlled the House for eight years before losing the majority in the chamber in the 2018 midterms amid a wave by House Democrats. But while Republicans lost the White House and their Senate majority in the 2020 contests, in the battle for the House they defied expectations and took a big bite out of the Democrats’ majority in November’s elections and currently only need a net gain of five seats in 2022 to regain control of the chamber.

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The autopsy also calls for looking at new ways to interpret polling to understand who is and who isn’t voting, and urges a rethinking of a media strategy that may have over-relied on TV ads during the 2020 cycle.

And Rep. Sean Patrick Maloney, the chair of the Democratic Congressional Campaign Committee who oversaw the analysis, predicted that with Trump not on the ballot in next year’s midterm elections, "there's no evidence that Republicans’ current message, which is divisive and reckless, will be able to recreate the turnout Republicans saw in 2020, and it might in fact hurt them."

The 52-page PowerPoint presentation, which was shared with House Democrats during a call Tuesday evening, included interviews with campaign officials, candidates, consultants and staff, as well as an analysis of over 600 polls from House races last year, according to a summary of the report obtained by Fox News on Wednesday.

"House Democrats are committed to protecting our majority to keep delivering real results to the American people, and that means learning the lessons of the last election and understanding where we can do better," Maloney, D-N.Y., explained in a statement to Fox News. "Our extensive Deep Dive is designed to help us do more of what we found works and less of what doesn't."

Maloney emphasized that "it’s important that we take lessons from this Deep Dive to strengthen our campaigns and better engage with voters ahead of next November."

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The study spotlighted that national polling – as it did in the 2016 election – once again underestimated the turnout of Trump voters, which means that the Democrats’ models of who would vote in the 2020 congressional elections were far more left-leaning than the actual electorate last November. The report points to considering new methods to better interpret polls and to get a better measure of those who won’t take part in surveys.

Rep. Katie Porter of California, who assisted in the autopsy, noted that the "deep dive helped us get an understanding of what went wrong with polling, and how Democrats can avoid these inaccuracies moving forward in 2022. We’re retooling our polling methods to get a more accurate sense of likely electorates, particularly in communities of color."

The report also noted that while the House Democrats had TV spending advantages over their GOP rivals last year, it didn’t always translate to wins at the ballot box, noting that some of the ad spending on TV in the final weeks leading up to the election was essentially wasted money. And it pointed to more diversity of platforms when it comes to campaign ad expenditures going forward.

Maloney, in an interview with The Washington Post, which was first to report on the autopsy, acknowledged that the GOP attacks against the "defund the police" movement and tagging Democrats as "socialists" proved to be more effective than Democrats ever anticipated. "The lies and distortions about defund and socialism carried a punch," he said.

Heading into November’s elections, House Democrats were predicting pickups. And the setbacks that materialized sparked a debate between the party’s progressive and moderate wings whether the push by lawmakers on the left on multiple social issues saddled Democratic incumbents in swing districts. 

"We spent a bunch of time understanding how to respond more effectively, knowing that they’re going to do it again," Maloney told The Washington Post.

But Maloney argued that the attacks by the GOP may not be as effective in 2022, when Trump’s not on the ballot.

"I don't think you can evaluate the effectiveness of their [Republican] false attacks without considering how the Trump turnout made those lies look more impactful than they might otherwise have been," the DCCC chair said in a statement to Fox News.

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The presentation also called for better outreach to minority voters.

"This is about acknowledging Democrats have work to do when it comes to communicating with communities of color, especially as we learn to better differentiate between the needs and concerns of the diversity that exists within our communities," Rep. Nikema Williams of Georgia, who also assisted on the report, said. 

"We’re doubling down on the investments we made in 2020 to hear from communities of color by ensuring we reach the breadth and depth of the Democratic coalition."