It’s happened in other states with open primary elections. Republicans, having already determined their presidential nominee, are crossing over in large numbers to vote in the Democratic primary.

In Virginia, eight percent of voters in the Democratic primary were self identified Republicans.

In some parts of Texas, almost a quarter of voters with a history of participation in GOP primaries asked for Democratic ballots.

In Ohio, where you can switch your affiliation on Election Day if you pledge your future loyalty to your new party, so many voters asked for Democratic ballots that some precincts ran out of them by afternoon.

Election officials may want to prepare for something similar in Indiana on May 6, which is being described as the first presidential primary in a generation that will actually mean something. For Democrats anyway.

And therein lies a dilemma. What’s a Republican to do on an otherwise dull primary day?

“I would hope that Republicans would stay in the Republican primary,” says Dan Parker, chair of the Indiana Democratic State Central Committee.

For one, he says, other offices are on the ballot that day and it is a partisan responsibility to select nominees in those races.

Secondly, Parker says, Democrats won’t tolerate it if Republicans attempt to make mischief. “They can be challenged and they will be challenged. We’re not going to allow Republicans to try to interfere with other races.”

As a technical matter, Parker’s right: Voters can be challenged for switching party affiliation at the polls. But in an open primary system like ours, citizens can pretty much do what they please as long as they sign an affidavit. There’s no such thing as a “registered” Republican or Democrat. You are what you say you are when you request a ballot at the poll.

It is a matter of public record, however, so doesn’t claim a party unless you’re willing to be publicly identified as such. A voter’s ballot choice is recorded on the poll list. Those lists are used by the parties and candidates to identify potential supporters.

In Ohio, a voter who changes parties must actually swear allegiance to that party, a higher standard of loyalty than Indiana’s, which didn’t stop thousands of Republicans from crossing over in that state’s March 4 primary.

The Cleveland Plain Dealer reported that in a single county, Cuyahoga, more than 6,000 Republicans asked for Democratic ballots. Lying on the pledge is a felony, punishable by up to 12 months in prison and a $2,500 fine.

After the election, the newspaper interviewed Republicans who crossed over and none had been challenged, including five who admitted they didn’t plan on being lifelong Democrats. A professor of political science told the newspaper a few thousand Republican crossovers wouldn’t have affected the outcome anyway since Hillary Clinton handily defeated Barack Obama.

No matter what the law allows, are there ethical-moral reasons for Republicans to avoid the temptation to jump into the Democratic fray? If the goal is to cause continued chaos within the Democratic nomination process, as conservative talk radio host Rush Limbaugh has laughed about with listeners, is it wrong?

Not at all, says Greg Garrison, conservative talk show host on Indianapolis radio station WIBC. “This is an old-line trick the Democrats do in open primaries across the country. They have patented the process.”

“All Rush has done is say what’s good for the goose is good for the gander.”

An obvious exception would be if Republicans, in crossing over, failed to vote in a contested primary. “Worry about your own party first,” Garrison advises. On May 6, Republicans do have a choice to make in six of nine congressional districts, eight state senate districts and 18 state House districts.

While some in Texas, Ohio and elsewhere may have been heeding Limbaugh’s advice, a pollster for Fox News found that others were voting Democratic because, after eight years of Republican control of the White House, they wanted a fresh start. Some wanted to cast an historic vote for a black man or a woman. A caller to Garrison’s show speculated that Hoosiers might vote for Hillary Clinton because they like Evan Bayh and it would increase the chances of him becoming a vice presidential candidate.