Or maybe it's four.

Virginia Eismann, a homemaker whose husband runs a wood-flooring business, said she wasn't sure whether their younger son, a 21-year-old college student, submitted his voter form in time.

If he did, "then there's one more of us," she said.

The Eismanns, of the Doylestown area, are among the tidal wave of people in the five-county Philadelphia region - former Republicans, former independents, former nonvoters - who registered as Democrats to vote in Tuesday's primary. And the majority of these newly registered voters appear to support Sen. Barack Obama, according to a recent poll.

The headlines are well-known: For the first time in decades, Democrats outnumber Republicans in Montgomery and Bucks Counties. And Democrats and independents, grouped together, now outnumber Republicans in the two remaining suburban counties: Chester and Delaware.

But the significance of the Democratic gains goes far deeper.

A close analysis of state voter-registration data from April 6 compared with April 2007 shows just how sweeping the changes are.

Democrats increased their party enrollment in 99 percent of the zip codes in the region, while the number of Republicans declined in 92 percent of zip codes.

Independents, many of whom have been voting as Democrats for years in fall elections, switched in large numbers to get a piece of the primary action in the race between Obama and Sen. Hillary Rodham Clinton. The number of independents dropped in 90 percent of zip codes.

At the same time, the Democrats continued a decade-long trend of gaining the upper hand, registration-wise, in more and more townships and boroughs.

Among the 238 municipalities in the five-county area, Republicans still hold a plurality in 181. But compared with this time last year, the Democrats have become top dogs in 15 additional municipalities - for a total of 57.

The biggest of the communities that have flipped party plurality since this time last year is Upper Dublin Township in Montgomery County. There, percentage-wise, the Republicans held a 45-41 advantage last April. Now, they are at a 41-46 disadvantage.

Other communities that have flipped include two townships similar to Upper Dublin - Plymouth and Whitemarsh, both classic, postwar suburbs near the border with Philadelphia.

Also on the list are a wide range of older boroughs - crossroads towns that run from economically modest Eddystone and Hulmeville to well-off Doylestown.

John J. Kennedy, associate professor of political science at West Chester University, noted that each of the 15 communities with a new Democratic registration edge voted for Democrat John Kerry over President Bush in 2004.

"People change their voting patterns first," he said. "It may take years - decades - before they change their registration, and then usually there is some watershed event to make it happen."

The Obama-Clinton race appears to be just such an event - not only in the region, but statewide.

Pennsylvania now has 8.3 million voters, of whom 4.2 million are Democrats and 3.2 million are Republicans. The Democrats have gained 326,756 voters since a year ago, and the Republicans have lost 73,009.

In the five-county Philadelphia region, the Democrats gained 140,000 voters and the Republicans lost 42,000 over the last year.