In the two months since Pennsylvania's April 22 primary, Democrats have added more voters than Republicans in all but five of the state's 67 counties and increased their statewide lead by 40,566 voters by the end of last week.
Republicans have lost nearly 1,500 registered voters since the primary.
The trend is especially pronounced in Philadelphia's suburbs, where Democratic leads acquired in Montgomery and Bucks Counties in the primary season have already grown. In Montgomery County, Democratic Commissioner Joseph M. Hoeffel III reacted with some glee to numbers that showed his party had increased its advantage from 10,001 voters on April 22 to 13,784 as of yesterday.
"It should humble some of the braggarts of the Republican Party," he said, "and confirm that the county is changing."
The continuing Democratic groundswell appears to challenge the notion that the primary voter rolls were distorted by Republican stalwarts who made a temporary switch to affect the Democratic outcome. If Republicans who crossed over to vote in the Democratic primary are returning to the fold, their numbers appear to be subsumed by Democratic gains.
"That's part of the long-term trend," Chris Borick, a professor of political science at Muhlenberg University, said of the post-primary Democratic registrations. "The primaries were, if you look at it, a peak or a little bit of a spike, but they weren't some kind of outlier event."
In several counties, Republicans are just beginning to move to try to recapture lost ground.
Republican U.S. Rep. Jim Gerlach's campaign began a "huge voter-registration test pilot program" to target Chester County ex-Republicans only two weeks ago, said Mark Campbell, his political director.
In Bucks County, where Democrats outnumbered Republicans by 3,706 on April 22 and by 6,620 as of Saturday, GOP leaders haven't yet begun a planned effort to shepherd home their lost sheep.
"We haven't pushed yet to send out letters and talk to them," said Harry Fawkes, Bucks County's Republican chairman for 36 years. "A lot of them, we're hoping, will come back. I can't predict it. We're going to try to do it."
There is no widespread optimism among Republicans that the effort will stem the Democratic tide.
In part, that's because the post-primary numbers are markedly one-sided. The largest Democratic voter gain in a single county was in heavily Democratic Allegheny, where the lead over Republicans has increased by 4,016 since April 22.
By contrast, of the five counties where Republicans added more voters than Democrats, the largest differential was 23 voters in Indiana County.
In each of the five counties where Democrats gained most - Allegheny, Philadelphia, Montgomery, Berks and Delaware - they added more than 3,000 voters.
Also, with no party primary looming, estranged Republicans do not seem to have much motivation to change back their registration. In the post-machine era of many Pennsylvania counties, showing fealty might be just an empty gesture.
"I'm just not sure that people consider registration as important as in the past," said Bob Asher, the longtime state Republican power broker. "There's just a lot more people that vote more of an independent streak and not necessarily a straight party, so they don't really feel that's important."
Oct. 6 is the deadline to register to vote in the November election.
The tide of Democratic registrations in the Philadelphia suburbs has not been matched by new independent or third-party registrations, suggesting that the change may be decidedly partisan. Montgomery County, for example, has gained about 1,000 more Democrats since April 22 than it has independent and third-party registrants combined.
"It's become expected now, but even three or four years ago it seemed really unlikely that Montgomery County would be a place where Democrats are becoming the majority," Borick said. "Think about Pennsylvania long-term. That just seems to be a sea change."