For the first time anyone can remember, Dauphin County is blue.

Buoyed by an onslaught of voter registrations, registered Democrats have overtaken the GOP in a county that local politicians said has been solidly Republican since the Civil War. As of Thursday, there were 81,489 Democrats and 81,340 Republicans -- a difference of 149 voters.

Even Diane Bowman, the head of the Dauphin County Democratic Party, said the development was unexpected.

"I don't think we could have anticipated that all of the pieces would have been aligned quite so perfectly," she said.

The Democratic presidential primary clash between Sens. Hillary Rodham Clinton and Barack Obama brought an unprecedented number of voters to the polls.

Voters switching to the Democratic Party is part of a long-term trend in Pennsylvania, said Chris Borick, an associate professor of political science at Muhlenberg College. The Democratic gains and Republican losses are "much more systematic" than merely a recent rash of voters switching to vote in the Clinton-Obama matchup, he said.

"It's not just an artifact from the spring," he said.

Longtime Republican strongholds in the Philadelphia suburbs of Bucks and Montgomery counties also have turned from red to blue, Borick said.

"Dauphin County would be the latest feather in the cap of the Democratic Party's resurgence," Borick said.