When Peter Meijer voted to impeach Donald Trump, breaking with nearly all of his Republican colleagues in one of his first acts as a newly elected member of Congress, Democrats praised him as the kind of principled conservative his party – and the nation – desperately needed.

But this election season, as Meijer fought for his political survival against a Trump-endorsed election denier in a primary contest for a Michigan House seat, Democrats twisted the knife and helped his extremist opponent win.

It is part of a risky, and some say downright dangerous, strategy Democrats are using in races for House, Senate and governor: spending money in Republican primaries to elevate far-right candidates over more mainstream conservatives in the hope that voters will recoil from the election-denying radicals in November.

In Michigan, the gamble paid off – for now. Meijer lost after the House Democrats’ official campaign arm spent $425,000 to elevate Meijer’s opponent, John Gibbs, a former Trump administration official who asserted, falsely, that Joe Biden’s victory was “simply mathematically impossible”.

It is impossible to know what impact the Democrats’ ad had on the race, but cost more than the Gibbs campaign raised.

Now, as the primary season nears its conclusion and the political battlefield takes shape, Democrats will soon learn whether the gambit was successful. While election deniers have prevailed in Republican primaries across the country without any aid from Democrats, critics say the effort has already undermined the party’s grave warnings about the threats to democracy.

“It is immoral and dangerous,” said Richard Hasen, a UCLA law professor and director of the Safeguarding Democracy Project. He said the risk of miscalculation was great, particularly at a moment when the January 6 committee is attempting to show just how destructive Trump’s stolen election myth has been for American democracy.

“It’s hard for Democrats to take the high road when they’re cynically boosting some of these candidates in order to try to gain an advantage in the general election,” he said. “That doesn’t mean that what Democrats are doing is as bad as what Republicans are doing, but it still makes it objectionable.”

Meijer’s defeat has fueled a sharp debate among Democrats over the potential perils of the tactic, especially as the party warns of the risks posed by these very Republicans. But others argue it’s a necessary and calculated gamble in pursuit of keeping a dangerous party from winning power.

“If you let Republicans back in power, it is going to be those Maga Republicans who are going to take away your rights, your benefits and your freedom,” Congressman Sean Patrick Maloney, chair of the Democratic Congressional Campaign Committee, said, defending the strategy in a recent interview on MSNBC’s Morning Joe. “We need to stop it.”

The president’s party historically loses ground during the midterms. Decades-high inflation and widespread frustration with leaders in Washington have dragged Joe Biden’s approval ratings to record lows, hampering Democrats’ efforts to preserve their razor-thin majorities in Congress.

The ads are ostensibly scripted as an attack – highlighting a candidate’s loyalty to Trump and their conservative views on abortion. In Michigan, for example, Democrats charged that Gibbs was “handpicked by Trump to run for Congress” and “too conservative” for the district. But when aired during a primary, the message is intended to appeal to the conservative base.

“The voters in the Republican primary had agency,” said Bill Saxton, the Democratic party chair in Kent county. “They had two choices.”

Saxton, whose county is situated in the west Michigan district, said it was now time to set aside the bickering over tactics and focus on the real threat: Gibbs’s extremism.

In 2020, Gibbs could not win Senate confirmation to direct Trump’s Office of Personnel Management over past comments he made, among them calling Democrats the party of “‘Islam, gender-bending, anti-police, ‘u racist!’”.

Democrats’ efforts to pick their opponents extends far beyond a single Michigan House race. They have deployed this strategy in House, Senate and governor’s races across the country.

In Maryland, the Democratic Governors Association boosted Dan Cox, who attended the January 6 rally and called Vice-President Mike Pence a “traitor” for not stopping the congressional certification of Biden’s victory as Trump wished. He won the party’s nomination for governor. That was after Democrats’ spent millions of dollars to successfully promote the Trump-backed election denier in the Illinois Republican gubernatorial primary. Both states lean Democratic and the party is reasonably confident their candidate will prevail.

The race causing the most angst is in battleground Pennsylvania. There the Democratic nominee for governor, Josh Shapiro, spent hundreds of thousands of dollars in TV ads boosting the rightwing extremist Doug Mastriano – far more than the candidate spent on his own campaign. Mastriano, who attended the January 6 rally and has cast doubt on the legitimacy of the 2020 election, is now the Republican nominee in a swing state where the chief elections officer is appointed by the governor.

Polls show a tight race.

The strategy hasn’t always worked. In California, the incumbent Republican congressman David Valadao narrowly beat back a rightwing challenger despite Democratic spending on ads that highlighted his vote to impeach Trump.

And in Colorado, an outside group aligned with Democrats spent millions to boost an election denier who marched to the Capitol with rioters on January 6 over a relatively moderate Republican, businessman Joe O’Dea, in the race to take on the Democratic senator Michael Bennet. O’Dea won and now the resources Democrats spent to make him unpalatable to the Republican base may help him appeal to moderate and independent swing voters.

Meddling in the opposition’s primary is not a new tactic. In 2012, Claire McCaskill, then a Democratic senator from Missouri, was facing a difficult re-election in a state where Barack Obama was deeply unpopular.

Surveying her prospective opponents, she devised a plan to lift the one she thought would be the weakest candidate, the far-right congressman Todd Akin. It worked: he won the primary, and she beat him decisively in the general.

But a decade later, she is urging caution.

“This has to be done very carefully,” she told NPR, adding: “You also have to be careful what you wish for.”

Maloney, the DCCC chair, has said the committee has a “high bar” for meddling in a Republican primary, but insisted that there are races where it “does make sense”. Still, it has become an issue for Maloney in his own primary race, where his challenger, Alessandra Biaggi, has accused him of playing “Russian roulette with our democracy”.

Some Democrats have also expressed misgivings about punishing the few Republicans willing to stand up to Trump. David Axelrod, a longtime Democratic strategist and political adviser to Barack Obama, said Democrats’ involvement in Meijer’s primary “makes them an instrument of Trump’s vengeance”.

Trump’s support has been one of the most decisive factors in choosing the party’s standard bearers, not Democrats, said David Turner, a spokesman for the Democratic Governors Association. In these races, he said Democrats seized the opportunity to expose a prospective opponent’s extremism early and pre-emptively blunt any attempt to “pivot” toward the mainstream during the general election.

Turner blamed Republican leaders for being “too cowardly to tell their voters the truth” about the 2020 election, a failure that he said ensured the success of election-deniers in the GOP’s 2022 nominating contests.

In Pennsylvania, one of Mastriano’s chief rivals was Lou Barletta, a signatory to the state’s fake elector scheme. And in Colorado, the candidate deemed more moderate won the Republican primary for governor but then selected an election denier to be her running mate.

“There aren’t any Liz Cheneys running for governor,” he said, referring to the Republican vice chair of the January 6 committee who may lose her primary over efforts to hold Trump accountable. “In terms of gubernatorial candidates, the scary part is that all these Republicans are regurgitating the same Maga talking points.”

Still, some Democrats argue that they are being held to a different standard than Republicans, who have failed to hold Trump and loyalists in Congress accountable. They say Republicans often cheer their leaders for being ruthless while Democrats are criticized for refusing to play hardball, especially when the stakes are the highest.

As a result of gerrymandering, Republican dominance of the redistricting process and historical trends, Democrats see few opportunities to flip House seats this cycle. Michigan’s third congressional district is one of them.

Gibbs has downplayed the impact of the ads, and projected confidence that he can win in November.

Hillary Scholten, the Democrat who will face him in the Michigan House race and had no involvement in the DCCC’s decision, called the focus on her party’s tactics an unwanted distraction from the issues voters care most about.

Scholten said: “It is the Republicans that decided who they wanted in their primary, and they chose John Gibbs, an extremist that embraces conspiracy theories and is way out of step with west Michigan. I’m focused on making sure he doesn’t get to Congress.”

Her newly redrawn Michigan district is considerably more favorable to Democrats this cycle than it was two years ago. And many Democrats believe Scholten, a former justice department attorney in the Obama administration who came close to beating Meijer in 2020, would have been a strong contender in a rematch.

While many are confident she can beat Gibbs, those still haunted by Trump’s against-the-odds victory in 2016 fear that in a “wave” election, Republicans deemed unelectable could be swept to power.

On the eve of his primary race, Meijer lashed Democrats in an online essay that accused them of “sell[ing] out any pretense of principle for political expediency”.

“Republican voters will be blamed if any of these candidates are ultimately elected,” Meijer wrote in an online essay published on the eve of the primary, “but there is no doubt Democrats’ fingerprints will be on the weapon. We should never forget it.”