ATLANTA — One look at the results of Georgia’s primary election last week led many Republicans to believe it was the product of Democratic meddling. Former President Donald J. Trump’s recruited challengers lost in grand fashion in his most sought-after races: David Perdue was routed by Gov. Brian Kemp by more than 50 percentage points, while Representative Jody Hice fell to Secretary of State Brad Raffensperger by nearly 20.
Mr. Trump and his allies pointed to so-called Democratic crossover voters as the cause of their shellackings. In Georgia’s open primary system, Democrats and Republicans can vote in the other party’s primary if they wish, and more than 37,000 people cast early ballots in this year’s Republican primary election after voting in the Democratic primary in 2020.
Some Democrats, for their part, staked a claim to these voters, arguing that they had crossed over to strategically support candidates who reject Mr. Trump’s falsehoods about the 2020 election. Most of the crossover voters, the Democrats said, would return to the party in November.
But a closer look at these voters paints a more complicated picture. Just 7 percent of those who voted early during last month’s Republican primary cast ballots for Democrats in that party’s 2020 primary election, according to the data firm L2. And 70 percent of this year’s crossover voters who cast early ballots in the G.O.P. primary had participated in both Democratic and Republican primaries over the last decade.
These voters, data suggests, are less Republican traitors or stalwart Democrats aiming to stop Trump loyalists than they are highly sought-after — and unpredictable — swing voters.
“I didn’t want any of the Trumpsters becoming a candidate,” said Frances Cooper, 43, who voted in Columbia County, two hours east of Atlanta.
A self-described moderate, Ms. Cooper said that she had voted in both Democratic and Republican primaries in the past, and that she could often vote “either way.” This time, she said, Mr. Kemp had been “pretty good, and was the best of our options.” She was undecided about the November general election for governor, but “if anything leaning toward Kemp.”
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Voters like Ms. Cooper base their choices in every election on multiple variables: their political leanings, how competitive one party’s primary might be or the overall environment in any given election year, among others. Some Democratic voters in deep-red counties opted for a Republican ballot because they believed it would be a more effective vote. Others, frustrated with leadership in Washington, voted according to their misgivings.
Many unknowns still remain. The current data on crossover voters includes only those who cast ballots during Georgia’s three-week early voting period, when the most politically engaged people tend to vote. In addition to traditional swing voters or disaffected Democrats, a portion of those who crossed over were indeed probably Democratic voters switching strategically to the Republican primary to spite the former president.
Yet the crossover voters who cast early ballots in last month’s Republican primary are not demographically representative of Georgia’s multiracial Democratic base, which also includes a growing number of young voters. Fifty-five percent of these early crossover voters were above the age of 65, and 85 percent were white, according to voter registration data. Less than 3 percent were between the ages of 18 and 29.
It is unclear whether a majority of these voters will return to support Democrats this November, as some in the party expect, or whether they will vote again for Republicans in large numbers.
“I think there’s a real danger on the part of Democrats in Georgia to just assume that they aren’t going to lose some of those voters from 2020,” said Erik Iverson, a Republican pollster who works with Georgia campaigns.
Crossing the runoff threshold
No race has attracted more debate about crossover voting than the Republican primary for secretary of state, in which Mr. Raffensperger, the incumbent, who had rejected attempts to subvert the 2020 election, defeated Mr. Hice, a Trump-endorsed challenger.
Though Mr. Raffensperger won by almost 20 points, he escaped being forced into a runoff election by finishing with 52.3 percent of the vote, or 2.3 percent above the majority threshold that would have prompted a runoff.
Operatives on both sides of the aisle have speculated that crossover voting was a chief reason that Mr. Raffensperger avoided a runoff. But drawing such a conclusion ignores the many reasons for crossover voting in Georgia, and probably overestimates the number of true Democrats voting for Mr. Raffensperger.
“That would be an awful lot of crossover voting,” said Scott H. Ainsworth, a professor of political science at the University of Georgia, adding that Mr. Raffensperger’s nearly 30,000-vote margin to avoid a runoff had most likely been spurred by more than just meandering former Democratic primary voters.
Still, that hasn’t dissuaded some from pointing to crossover voters as a root cause of Mr. Raffensperger’s success.
Representative Adam Kinzinger of Illinois, a Republican who founded the group Country First, which supports pro-democracy G.O.P. candidates, cited the Georgia secretary of state’s victory as proof of his organization’s effectiveness.
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“I have no doubt we made the impact,” Mr. Kinzinger said. His group distributed mailers, sent text messages and ran television ads in support of Mr. Raffensperger. The group’s message to Georgia Democrats, who had largely noncompetitive races for governor and Senate, was to vote in the Republican primary instead. Mr. Kinzinger said the efforts helped Mr. Raffensperger avoid a runoff.
The organization has tried to lift candidates in states including Texas and North Carolina, where it successfully helped to oust Representative Madison Cawthorn. The group has plans to support candidates in Michigan and to defend Republican incumbents like Senator Lisa Murkowski of Alaska and Representative Liz Cheney of Wyoming.
Sometimes, the motivation for Democrats or Republicans to cross over into the other party’s primary goes deeper than statewide contests. For example, if voters are drawn into a noncompetitive district, they will sometimes vote in the other party’s primary if it will essentially determine the general election winner.
Take Clarke County in Georgia. Home to Athens, a Democratic-leaning city, the county is wholly contained in the 10th Congressional District, a decidedly Republican seat held by Mr. Hice (he did not run for re-election because he was running for secretary of state). In Clarke County, roughly 900 voters who cast early ballots in the Republican primary had voted in the Democratic primary in 2020, one of the largest county totals of crossover voters outside the Atlanta area.
Those voters, however, may not have been focused on the statewide races but on the closely contested primary election to replace Mr. Hice. Whoever prevailed in the multicandidate Republican primary was likely to win in November in a district that Mr. Hice carried by 25 points in 2020.
“There’s a lot of Democrats in Athens and Clarke County who will have no meaningful voice in their choice for Congress unless they vote in the primary,” said Anthony Michael Kreis, a law professor at Georgia State University. “There are probably some Democratic voters who were just voting quite rationally in the sense that they wanted their voice heard in a House race, and that is their only meaningful opportunity to do so.”
Nate Cohn contributed reporting.