The top two contenders for the Republican presidential nomination are accusing each other of benefiting from the support of crossover Democratic voters in states that allow anyone to participate in a party primary.
And both are correct. Mitt Romney and Rick Santorum have each worked to woo independent voters and conservative Democrats during campaign appearances. While it may be anathema to their hard-core GOP supporters, it's an acknowledgement of the kind of crossover appeal that any GOP nominee will need in November if he's to defeat President Barack Obama.
It also creates a tricky rhetorical tightrope for the candidates: making a pitch to non-Republican voters while finding fault when an opponent does the same thing.
When Santorum made the Michigan primary a squeaker this week, for example, Romney attributed his rival's strong second-place finish to help from liberals who hoped Santorum would make a weaker opponent for Obama.
"They got the news from everyone from Michael Moore to Barack Obama's team to, frankly, Rick Santorum as well, saying, `Go play mischief in the Republican Party. Vote against Mitt Romney and try to give this to Rick Santorum.' You know, they don't want to face me in the fall. They'd rather face Rick Santorum," Romney said in a recent interview. "They came in, in large numbers, and voted for Rick."
Santorum did get a boost from Democrats; 13 percent of his votes came from them, according to exit polls, compared with 4 percent for Romney.
And when Romney cruised to a lead-off win in New Hampshire, Santorum discounted it by saying the victory came from an electorate in which only a minority was Republican.
Indeed, in exit polls in New Hampshire, 53 percent of respondents didn't identify themselves as Republicans. Overall, Romney received 62 percent of his support from Republicans, 2 percent from Democrats and 36 percent from independents.
Those numbers are virtually identical to the partisan breakdown of Santorum supporters in New Hampshire: 65 percent Republican, 2 percent Democratic and 32 percent independent. But Santorum placed a distant fifth.
In other words, each is giving the other too much credit for crossover appeal, and neither is pure on the subject.
"We want the activists of the party _ the people who make up the backbone of the Republican Party _ to have a say in who our nominee is, as opposed to a bunch of people who don't even identify themselves as Republicans picking our nominee," Santorum told Minnesota voters on a conference call on Jan. 29. "I don't like that. I believe that states should only allow Republicans to vote in Republican primaries."
He said that if voters want to participate in the GOP contest, they should switch their party identification.
Santorum changed his tune a month later in Michigan, sending automated calls to Democrats encouraging them to turn out for him.
"Michigan Democrats can vote in the Republican primary on Tuesday. ... On Tuesday, join Democrats who are going to send a loud message to Massachusetts' Mitt Romney by voting for Rick Santorum for president. This call is supported by hardworking Democratic men and women. Paid for by Rick Santorum for president," the call said.
Choosing to participate in another party's primary, while not common, can be a strategic choice for voters. Conservative talk radio host Rush Limbaugh urged his listeners to do that in 2008 to prolong the Barack Obama-Hillary Rodham Clinton primary season in what he called "Operation Chaos."
Romney himself did the same thing in 1992, voting for Democrat Paul Tsongas in Massachusetts' Democratic primary.
"In Massachusetts, if you register as an independent, you can vote in either the Republican or Democratic primary," Romney told ABC News. "When there was no real contest in the Republican primary, I'd vote in the Democrat primary, vote for the person who I thought would be the weakest opponent for the Republican."
Romney spokeswoman Gail Gitcho defended the practice and said "there's really no comparison at all" to Santorum, who reached out to some of those Democrats.
The rivals are unlikely to let the issue rest.
"If you're running for president to be the conservative voice, you don't seek union, liberal votes when your campaign is desperate," said Georgia Attorney General Sam Olens, a Romney supporter.
Countered Santorum spokesman Hogan Gidley: "We figured if we can get them in the primary, we can keep them in the general."
Saturday's GOP caucuses in Washington state are open to voters from either party, as are six of the 10 states that have contests on Super Tuesday: Alaska, Georgia, Massachusetts, Tennessee, Vermont and Virginia. Only Romney and Ron Paul are on the Virginia ballot.
AP Deputy Director of Polling Jennifer Agiesta contributed to this report.