Sen. Bob Casey (D., Pa.) promised to "fight like hell" against the Republican push to repeal and replace the Affordable Care Act, and urged voters to do the same Sunday at a town hall meeting in Philadelphia.

The crowd cheered and held up signs reading "Agree" as he spoke out on the battle over the health law often called Obamacare.

The fiery words from Casey and supportive reaction from the audience, in response to the first question he received, set the tone at the the senator's first town hall in years.

Casey, wearing jeans and a pullover sweater, took questions from constituents in a dimly lit auditorium at the Penn Museum at the University of Pennsylvania. The event made him one of the few lawmakers from the Philadelphia region to host a town hall meeting since President Trump's election. 

It came as Casey gears up for a potentially challenging re-election campaign next year, as activists on the left have caused rowdy scenes at Republican town hall meetings, and as liberal voters have demanded that lawmakers, including Pennsylvania's Republican senator, Pat Toomey, do more to face the public and stand up to Trump.

Casey, long known as a soft-spoken moderate, has more forcefully embraced liberal positions, and has vocally and visibly opposed the president. He stuck to that posture Sunday, much to the delight of the crowd that filled most the 750-seat auditorium in the heavily Democratic and liberal city.

Asked whether he would oppose any plan to take funding from Planned Parenthood, Casey quickly said, "Number one, yes, and number two, I already have."

Cheers broke out again.

Casey's office had supplied signs reading "agree" on one side and "disagree" on the other. The "agree" side was used almost exclusively. "Those signs are getting a workout," Casey said after they were flourished in response to one questioner who urged Trump to resign.

While the audience covered a wide range of topics, nearly all the questions were framed from a liberal perspective. Constituents asked how they could pressure their representatives, urged Casey to stand up to Trump's most controversial cabinet secretaries -- Education Secretary Betsy DeVos and Environment Secretary Scott Pruitt -- and called on lawmakers to fight climate change and protect education programs for people with disabilities.

Casey hedged on one issue: whether or not he would try to block Trump’s Supreme Court nominee, Neil Gorsuch.

"I have substantial, real significant, major concerns," he said, but added that he would not announce a final decision until after confirmation hearings later this month.

The only rebukes came when Casey failed to go far enough left. He drew scattered calls of "No!" for saying Pennsylvania should embrace both clean energy and fracking, rather than condemning fracking.

Several people said in interviews that they wanted to support the senator for taking the time to speak to constituents face to face. Unprompted, they used Casey's event to criticize Toomey, who has faced pressure to hold an in-person town hall meeting, but has not done so.

"I would have preferred a chance to speak with my Republican elected official, but I wanted to hear a lot of what Sen. Casey had to say," said Christina Jones, of Havertown.

Toomey and Republican U.S. representatives from the Philadelphia area have almost all avoided in-person town hall meetings, saying they fear events overrun by protesters trying to cause trouble. Many have instead taken questions in large teleconferences or through social media.

Jones said the in-person event helped her "feel a sense of community" with others who have the same concerns about Trump. But she also worried. Democrats, "just don't have the votes, so while I know he's trying, I'm still concerned."

A search of Casey’s website indicates that his last participation in a town hall was in 2011 -- the year before his last re-election.

Aides said he had held other public events in which he faced constituents. A spokeswoman said that he took questions in January at an open forum hosted by PennEnvironment, a liberal environmental group, and that constituents can sign up for regularly scheduled sit-downs with Casey over coffee in his Washington office.

His office said Sunday's event was to be the first of a series of town hall meetings across the state, with more dates and locations coming soon, including sessions outside the liberal Southeast.

"While this is a really good environment for him, it's going to be more interesting for him to go into the more red parts of Pennsylvania," said Regina Chusid, a recent law school graduate who interned for Casey in 2013 and attended Sunday's event. "It'll be good for him to get pushback."

Republicans, noting that Trump and Toomey both won statewide races in 2016, have eyed Casey as a potential target next year.

"Last November, Pennsylvanians loudly and clearly voted for change, but all Casey has to offer are more of the same failed policies of the last eight years," said Bob Salera, a spokesman for Republicans' Senate campaign arm, in an email.

Correction: A previous version of this story misspelled Regina Chusid's last name.