Specter, who switched parties earlier this year after representing Pennsylvania for decades as a Republican, and Rep. Joe Sestak, who has announced he will challenge Specter in next year's Democratic primary, both addressed the Netroots Nation convention in Pittsburgh, The Philadelphia Inquirer reported.
"I carried the president's message," Specter said. "I put my neck on the line."
In the last few days, Specter has held four town hall meetings in Pennsylvania, where he has been verbally attacked by opponents of the president's plan.
Sestak argued Specter cannot be trusted, as he opposed a public health-insurance option while a Republican, and described himself as "150 percent behind" the public option.
Specter, who was known as a moderate Republican, said he has a "reputation for candor and honesty."
"I'm not trimming my sails," Specter said. "I'll defend each of my votes one by one. I don't believe in these statistical generalizations."