When Ted Cruz, John Kasich, and Donald Trump square off in Pennsylvania's April 26 Republican presidential primary, they will find themselves competing for votes from a rapidly changing base.
At least 128,000 voters statewide have changed their registration since Jan. 1 to join the party. Nearly 85,000 of them had been Democrats; 42,000 were independents or third-party voters. The GOP has also racked up 55,468 more first-time registrants.
The changes reflect what experts are calling an unprecedented number of party switches before a primary election.
That raises questions: Are Democrats and other voters flocking to the GOP in support of one of its three candidates? Or could they be plotting to stuff the ballot boxes for a Republican they think their nominee can beat in November?
"I don't think we can say there's one reason here," said G. Terry Madonna, the veteran pollster who directs the Center for Politics and Public Affairs at Franklin and Marshall College. "But in the Philadelphia suburbs, if people are switching, some of that would be strategic: Vote for Trump because he would be the weakest candidate against [Hillary] Clinton."
Since the start of 2016, nearly 215,000 Pennsylvania voters have switched their party affiliation, which includes the GOP surge, as well as 86,500 who became Democrats.
At the very least, the shift underscores something different about this year's primary. The suspense of presidential races often ebbs before the Pennsylvania primary, but this year's April 26 contest still has meaning - especially on the Republican side of the ballot.
The unexpected significance is what motivated Erik Blomain, formerly an unaffiliated voter, to register as a Republican.
"Normally our primary doesn't matter a whole lot," said Blomain, a 28-year-old medical student at Jefferson University, who says he plans to vote for Kasich. "It kind of matters more than any primary in my lifetime."
Monday was Pennsylvania's deadline to register or change party registrations.
Pennsylvania has roughly 3 million registered Republican voters and 4 million registered Democrats. Another 676,000 are registered as unaffiliated, and as such, will be unable to vote in Pennsylvania's closed primary. State officials said they were unlikely to have a final tally for about two weeks.
But since March 21, more than 18,000 voters across the state, including more than 4,500 in Philadelphia and its neighboring counties, had switched party registrations, state data showed.
Party preferences often shift when the nation picks a new president after one party has held the White House for eight years. But experts say the tide of switchers may be unusually high this time.
"I've been doing this for a long time, and this is the first time in 30 years I've been asked about this," Madonna said.
While Pennsylvania's comparable figures for the last such presidential year, 2008, were not immediately available, the latest numbers far exceed those for all of 2014, when only about 28,000 voters statewide switched to each of the two major parties. For the GOP, that's a fifth of what the party has seen in the first three months of 2016. For Democrats, too, it's only a fraction.
This year's lower rate of voters switching from R to D than the other way around may arise from a perception that "the Democratic race is effectively over" between Clinton and Bernie Sanders, Madonna said. Still, the Democratic Party added more than 70,000 first-time registrants this year.
Instead, voters have turned their attention to the Republican race, where competition remains hefty. Droves of voters' switches to the GOP are likely motivated - positively and negatively - by Trump, Madonna said.
That theory was borne out by interviews with several newly minted Republicans on Monday.
Joan Albert, 70, of the city's Somerton section, was blunt when asked why she switched after years as a Democrat.
"I don't like Hillary Clinton," she said. "I'd rather vote for Donald Trump."
Her husband, Marvin Albert, also 70, said he and his wife appreciate Trump's freewheeling speeches, drawn to what they see as his unusually candid nature.
"He tells you what's on his mind," Marvin Albert said. "He's not always right with what he says, but at least he speaks with what he feels."
Diana Albano, a 77-year-old retiree from South Philadelphia, has also been persuaded to support the outspoken businessman, even though she had been a registered Democrat who voted for President Obama.
"I like that [Trump] says what he believes," Albano said, admitting that she finds his bluster off-putting sometimes. "I'm not crazy about his approach, but I just like his honesty."
The bombast, however, did not sit well with everyone.
Former Republican Brian Devlin, 26, a process chemist from Northeast Philadelphia, became a Democrat and Sanders supporter after being turned off by the divisive rhetoric of Trump and Cruz.
"I don't like the whole direction the party is going in," he said.
Christa Elliot, 25, of Washington Square West, also switched from Republican to Democratic because, she said, Trump was using hateful rhetoric to whip up votes.
"I'm a little concerned that he's even a candidate," she said.
Such voters can always switch parties again after the primary.
Madonna said the complex array of reasons behind the sudden surge in switches was likely no surprise. "There are a variety of motives going on here," he said.