Mark Critz successfully campaigned as an independent-minded Democrat willing to break with the party on critical issues like health care and cap-and-trade.

He began proving it Thursday night.

The successor to the late John Murtha was one of two Pennsylvania Democrats who voted against a repeal of  “Don’t Ask, Don’t Tell,” which would allow gays to serve openly in the military. He was joined by U.S. Rep. Chris Carney, a veteran himself who faces a potentially stern test this fall against Republican and ex-U.S. Attorney Tom Marino.

The repeal, which was an amendment spearheaded by Pennsylvania congressman Patrick Murphy, passed 234-194.

Repeal of the hot-button issue is widely popular with nearly all liberal Democrats and, in fact, the vast majority of Americans, according to many polls. But in culturally conservative western Pennsylvania, such a vote could be harmful.

Critz’s surprisingly comfortable special election victory over Republican Tim Burns is attributable at least in part to the fact he positioned himself as opposed to many of President Obama’s policies. Opposing them on his first major vote in Congress is a signal to voters he doesn’t plan to break that promise. It also doesn’t give Burns any potential ammunition when the two tangle once again in the general election.

The Pennsylvania delegation voted along party lines otherwise.