“It is my privilege to endorse Senator Specter,” Dinniman said in a campaign statement. “His knowledge and experience make him best suited to continue representing the citizens of Chester and Montgomery counties, and of Pennsylvania.

“And having the Senator at the top of the Democratic ticket this fall puts us in the best position to win,” Dinniman added.

“In order to win we have to get our Republican and independent friends to vote for us,” Dinniman said during an endorsement party here. “The majority and Republicans and Democrats in this county are right in the middle. They’re not the right wing that’s gaining control of the Republican Party and they’re not the left wing. They’re in the middle. And they’re might be nuances of difference but a candidate who appeals to that middle ground will win. … Manan appeals to that middle ground.”

Trivedi in September entered a primary that had appeared to be an open field for Doug Pike, the wealthy former Inquirer editorial writer who had already won the backing of much of the local Democratic establishment. Since then has impressed rank-and-file Democrats and party activists while quickly emerging as a viable challenger, even as he expects to be significantly outspent by Pike. The support of Dinniman, delivered at the home of last year’s Democratic nominee in the district, Bob Roggio, was Trivedi’s biggest endorsement nab to date. Dinniman is seen as a figurehead in Chester County Democratic politics, having helped bring the party of the doldrums over the last couple decades.

“I’m very honored and humbled to have Andy Dinniman’s support,” Trivedi told pa2010.com. “He was there when no one else was there.”

Trivedi said he was the candidate to win centrist voters because he believes in “evidence-based” policy.

“I believe in policies that work,” he said. “For some reason, D.C. is an evidence-free zone. But I am not an ideologue.”

See videos of Dinniman and Trivedi below:

Dinniman will throw his support to the Reading physician during an endorsement party later this month at the home of Bob Roggio, the Democratic candidate who lost in the district last year and is also backing Trivedi, according to an invitation obtained by pa2010.com. But unlike Roggio, Dinniman is a longtime elected official in Chester County with a significant political following, making him Trivedi’s most valuable supporter to date.

“I think Andy Dinniman is probably one of the most well-liked and influential politicians in Chester County,” Roggio said.

In a brief interview Wednesday, Dinniman said that Trivedi’s life story, his experience in the health care sector and his perceived ability to win in a general election all contributed to his endorsement.

“Here you have a person who grew up in this area, who is a hero with the marines, and a person who understands so well the problems in health care,” Dinniman said. “I just felt this was a compelling story.”

Dinniman also noted that Trivedi hails from Berks County, where Democrats have historically lost the district.

“Remember, if you look at the history of votes in this district, you need a person who has a connection and ability to win Chester and Berks counties,” he said.

Much of the Democratic establishment remains firmly behind Pike, a wealthy former editorial writer at The Inquirer. Incumbent members of Congress have endorsed and contributed to his campaign, and he is seen as having the implicit backing of the Democratic Congressional Campaign Committee. He got an early head start in building a campaign, and with the significant money he is pouring into his own candidacy, he is still widely perceived as the favorite.

But Dinniman’s endorsement is just the latest sign that local Democrats are enthusiastic about Trivedi’s candidacy. At least one party insider who had endorsed previously supported Pike walked back his endorsement when Trivedi entered the race, and rumors abound that more insiders might soon follow his lead. Trivedi also won the endorsement for former state Senator Connie Williams, a powerful presence in Montgomery County politics.

The endorsement party is scheduled for Nov. 15.

“We have a great opportunity in reclaiming the PA 6 in Manan Trivedi,” Dinniman says in the invitation. “His knowledge, his service to his community and country, both as a physician and an Iraq War veteran, have prepared him well for the halls of Congress.”

Whoever wins the Democratic primary will face the winner of a crowded GOP contest, with Democrats looking to capture the seat for the first time since it was drawn in redistricting earlier this decade.

•Earlier on pa2010.com: In PA-6, a Dem primary that wasn’t now emerges

“I haven’t ruled it out,” Roggio, the businessman and former Bob Casey staffer, told pa2010.com Tuesday.

Democrat Doug Pike has been building an early advantage in fundraising and endorsements, while Gerlach is running for governor. But Roggio said that regardless of whether he decides to run, it’s unlikely that Pike will march to the nomination unopposed.

“I do believe there will be a challenge to Doug Pike,” he said.

Roggio fared better than many had expected on Election Day last year, running up good numbers in Montgomery County and even starting the day with a lead as early election returns came in. But his support was sparse in the critical parts of the district in Berks and Chester counties, and he lost by about 4 points.

With Gerlach out, analysts widely agree that Democrats are more likely than ever to capture the seat. But with Pike moving fast, Roggio said any challenger will have to make a decision soon. State Senator Andrew Dinniman (D-Chester) is increasingly rumored to be seriously considering the race, but could not be immeidately reached this week.

“It’s getting to a point that it would have to happen within a week or so, because Doug Pike… has made a very good start,” he said.

Regardless of what happens, Roggio emphasized, what’s most important is that the party wins next November.

“This is an opportiunity for the Democrats this year,” he said. “It’s not going to be easy no matter what. But we have an opportuniy here and I’m hoping that, whichever way it goes, we make the most of it.”

State Representative Curt Schroder (R-Chester) and Chester County Recorder of Deeds Ryan Costello are both seeking the GOP nomination.

Doug Pike, a former editorial board member at The Philadelphia Inquirer, is the only Democrat to officially declare his candidacy for the seat, which includes areas of Chester, Montgomery and Berks counties. But at least three others are considering the race, including two who have challenged Gerlach before. The district has consistently been one of the most competitive in the state. And while Democrats think they can win even if Gerlach stays put, most analysts consider the seat a lock to switch parties if he pursues the governorship instead.

“He’s had a tenuous hold on it,” said G. Terry Madonna, a pollster and political science professor at Franklin & Marshall College. “Somehow, he’s found a way to win. I think it gives the Democrats a huge opening should he actually run [for governor].”

Democrats said to be considering the race include Dan Wofford, the son of former Senator Harris Wofford who ran against Gerlach in 2002; Bob Roggio, the Montgomery County businessman who narrowly lost to Gerlach last year; and state Senator Andrew Dinniman (D-Chester), the first Democrat to be elected in his district since the 19th Century. All three remain cautious about entering the race—and curious to see what Gerlach does.

“I think the seat remains very winnable, whether or not Jim Gerlach vacates it to run for governor,” said Wofford, who lost by less than 3 points in 2002. “I think he’s vulnerable, and the demographics of the district are more favorable than they were when I first ran.”

The district has become far more Democratic in recent years. Whereas Republicans outnumbered Democrats by about 30,000 votes in 2005, by earlier this year, Democrats held an edge of more than 20,000 votes. These margins have kept Gerlach from ever winning by more than about 4 points; he won by less than 1 1/2 points to against Lois Murphy in 2006. But even as it has grown more Democratic in recent years, Gerlach has managed to defend the district thanks to his long service as a state lawmaker in the area and to the reputation he has built, deserved or not, as a moderate Republican. In a recent interview with pa2010.com, Gerlach said he would win again if he sought reelection.

“They’ve spent over $15 million to beat me,” he said of local and national Democrats. “They haven’t done it, and they’re not going to do it.

“My voting record reflects what people in this district want from their representative in Washington,” he added.

In announcing his candidacy, Pike said Gerlach’s moderate image is a facade.

“Particularly at this time of economic crisis, I feel that he is a typical partisan Republican. a just-say-no Republican, not someone offering practical solutions to get us out of this economic crisis,” Pike said.

Wofford, who has been encouraged by friends and political supporters to run, would not comment specifically on whether he was actively considering it, but his name continues to be mentioned by party insiders. Dinniman, whose 19th Senatorial District includes West Chester, said he was focused for now on education reform in Harrisburg and would begin to think more seriously about the race later this year. Roggio said he was more likely to run if Gerlach didn’t, but was considering either possibility.

“I think the Democrats would have an excellent chance in 2010,” Roggio said.

Chris Casey, the brother of Senator Bob Casey, is also rumored to be considering the race, but could not be reached for comment. State Representative Curt Schroeder (R-Chester) has expressed interest in seeking the GOP nomination if Gerlach runs for governor.