It’s a replay of the cynical tactic Democrats employed in the 2022 midterm elections. Then, they spent more than $53 million across nine states’ primaries to boost far-right Republican House candidates who had questioned or denied the validity of Joe Biden’s victory in the 2020 election, as well as MAGA-inclined gubernatorial candidates in Maryland, Pennsylvania and Illinois.

There’s no question it paid off: Democrats hold several House seats they might not have otherwise and won all three governorships. There’s also no question it reeked powerfully, and enduringly, of hypocrisy. Who knows why so many Americans still back Mr. Trump despite his evident lies about 2020? But maybe one small part of the reason is that Democratic operatives keep manipulating the issue for short-term political advantage.

Mr. Moreno wasn’t always an election denier. He urged his social media followers to “accept the results” in late 2020 and tweeted on Jan. 6, 2021, that Mr. Trump deserved “lots and lots of blame for this.” But then he decided to run for office. “President Trump says the election was stolen, and he’s right,” Mr. Moreno said in a commercial during a short-lived 2022 bid for the Senate. More recently, he’s called those prosecuted for storming the Capitol “political prisoners.”

The Democratic commercial doesn’t mention any of that. Nominally, it’s an attack ad because it calls Mr. Moreno “too conservative” and mentions his support for a national abortion ban and repealing Obamacare. But those points appeal to GOP base voters. “Moreno would lead the charge to enact Trump’s MAGA agenda,” a narrator says. The spot says that the former president calls Mr. Moreno “exactly the type of MAGA fighter that we need.” A spokeswoman for Senate Majority PAC said in a statement that Ohioans “deserve to know the truth about Bernie Moreno.”

In the Ohio race, state Sen. Matt Dolan would be the strongest Republican candidate against Mr. Brown in November. He’s a governance-minded conservative in the mold of former senator Rob Portman and Gov. Mike DeWine, who both endorse his bid. (Mr. Dolan’s father owns the Cleveland Guardians; one reason Mr. Trump has attacked the son is that the baseball team changed its name from the Indians.) Mr. Dolan would likely be a vote in the Senate for aiding Ukraine, which has a large diaspora in Ohio, while Mr. Moreno is critical of sending any more money. So the Democratic push for Mr. Moreno flies in the face of the party’s position on that crucial issue, too.

Polling shows the GOP primary within the margin of error, with Mr. Dolan opening a slight lead and Ohio Secretary of State Frank LaRose in a distant third. In a general election matchup, Mr. Brown leads Mr. Moreno but trails Mr. Dolan.

To repeat: Senate Majority PAC’s sole job is winning elections, so it’s rational for it to intervene in favor of Mr. Moreno. The $2.7 million buy is a drop in the ocean of likely spending on what could be this cycle’s most expensive Senate race. The group plans to air $65 million of television ads in Ohio during the general election while its Republican rival, Senate Leadership Fund, plans to spend $57.5 million.

But Senate Majority PAC’s tactics clash grotesquely with President Biden’s portrayal of the 2024 stakes in this month’s State of the Union address: “January 6th and the lies about the 2020 election, and the plots to steal the election, posed the gravest threat to our democracy since the Civil War,” he declared. Mr. Biden said those who stormed the Capitol “placed a dagger at the throat of American democracy,” adding: “The threat remains, and democracy must be defended.” The president called on lawmakers to “respect free and fair elections, restore trust in our institutions, and make clear political violence has absolutely no place in America.”

Mr. Trump has twice carried Ohio by eight points. The Moreno campaign points out that many Democrats assumed Mr. Trump would be the easiest Republican for Hillary Clinton to defeat in 2016. Whoever wins Tuesday’s primary — even Mr. Moreno — has a real chance of sitting in the Senate a year from now. Democrats should be careful what they wish for.