Democrats were caught napping in the 2010 election ahead of the last round of redistricting — and it cost them control of Congress for nearly a decade.

Now Republicans are warning the same thing could happen to them.

Senior Republicans concede they’re at risk of losing dozens of state-level elections that will determine who wields power over the post-2020 congressional map — and potentially which party controls the chamber for the following 10 years. While Republicans are establishing a massive national infrastructure devoted to reelecting President Donald Trump and winning congressional majorities, party officials say the state legislative races are being overlooked.

The trepidation comes as an array of well-funded Democratic groups — including one with the backing of former President Barack Obama and ex-Attorney General Eric Holder — are flooding cash into Virginia, a key redistricting battleground that's holding state legislative elections this fall.

Democrats are expected to plow tens of millions into races next year.

“This is as serious as a heart attack and we’ve got to do everything we can to win it because this isn’t about one cycle. It’s about the next decade. And our success nationally as a party is going to depend on our success in these states this cycle,” said Republican State Leadership Committee President Austin Chambers. He acknowledged that his party is less focused on statehouse contests than Democrats are.

“If we get beat in these state legislative races, in these judicial races in these critical states, our party is going to be in a bad position for the next 10 years,” Chambers added.

On Thursday morning, Chambers’ group will unveil an initiative to preserve the party’s fragile majorities in states like Pennsylvania, Florida and Texas. With multiple states closely divided between the two parties, he noted, the outcome of fewer than 50 legislative seats across the country could determine how a wide swath of congressional districts are redrawn.

The concerns about redistricting have reached the White House. Vice President Mike Pence’s team has been in touch with Chambers and is considering adding statehouse races to his campaign schedule. The vice president has raised money for Virginia Republicans and his aides are looking into the possibility of having him travel to other states, including North Carolina and Iowa.

The GOP's redistricting troubles represent a complete turnabout for the party. In the run-up to the 2010 election, Chambers’ group outspent its Democratic counterpart nearly 3-to-1, helping Republicans net nearly 700 seats and flip control of 20 legislative bodies. The party that year benefited from a broad backlash against Obama's first years in office, particularly his health care overhaul.

Republicans used their control of line-drawing to solidify and protect their newly won House majority, which remained intact through 2018.

This time around, it’s Democrats who are playing big. The Democratic Legislative Campaign Committee outraised the RSLC during the first half of 2019. And unlike a decade ago, Democrats are getting help from a galaxy of outside groups and allies, especially Obama.

The former president has lent his fundraising heft to the Holder-led National Democratic Redistricting Committee, which expects to pour more than $13.5 million into statehouse races this election cycle. Obama who took the unusual step in 2018 of endorsing state legislative candidates, has also folded his Organizing for America political organization into the Holder effort.

Republicans who were involved in the 2010 redistricting fight say they’ve been taken aback by the Democrats’ newfound focus on state legislative contests. Chris Jankowski, a former RSLC president who oversaw a pre-2010 initiative to compete in key legislative contests, called the Obama-endorsed group “well-funded and effective.”

“I know the RSLC is aware and fighting back, but it’s going to take a real commitment from national donors to focus beyond the White House,” said Jankowski, who is not involved in the current Republican fundraising effort.

Others warn that overlooking statehouse elections could have long-lasting implications for the party, which was wiped out in 2018 legislative elections.

“If Republicans don't start investing in state legislative races and the litigation and data needed to secure our majorities to the same extent the Democrats are, the GOP will see our legislative majorities erased and it will take decades to rebuild them,” said Adam Kincaid, executive director of the National Republican Redistricting Trust, the party’s data and legal clearinghouse for the next round of line-drawing.

The Democratic deluge is being felt most immediately in Virginia, where Republicans are trying to defend one-seat majorities in both legislative chambers. Democrats out-raised Republicans during the second fundraising quarter, and a handful of outside liberal groups, including the Michael Bloomberg-backed Everytown for Gun Safety Action Fund and the Tom Steyer-funded NextGen America, have pledged to spend more than $5.5 million combined ahead of the November contests.

Other Democratic heavyweights are getting involved, too. Former Virginia Gov. Terry McAuliffe, a former national party chairman and a fundraising powerhouse, has steered $400,000 to Virginia candidates through his political action committee.

McAuliffe, who has raised money for Holder’s group, said Democrats are making up for a longstanding failure to prepare for pre-Census elections.

“We’re organized for the first time when it comes to redistricting,” he said.

Some Democrats say the attention to down-ballot races reflects lessons the party learned after two devastating losses: In 2016, when it became clear it isn’t enough to just play in presidential elections, and in 2010, when they were devastated in state-level races.

“Back then, we thumped our chests at the victory of President Obama and an expanded majority in the House,” said former Rep. Steve Israel, a past Democratic Congressional Campaign Committee chairman. “Meanwhile, Republicans shrugged their shoulders and took the fight to state and local elections.”