Sen. Bob Casey was the only Democrat in a competitive 2018 race to sign onto a bill banning assault weapons, and Republicans wasted no time criticizing the move. 

The Pennsylvania Democrat has evolved on gun control issues since he was first elected in 2006. And Republicans are accusing him of misleading Pennsylvania voters.

“Bob Casey’s support for Senate liberals’ radical gun ban legislation is a slap in the face to the Pennsylvania voters he lied to about his views on the Second Amendment,” said Bob Salera, a spokesman for the National Senatorial Republican Committee. “It’s clear that Bob Casey’s allegiance is to Washington liberals and anti-gun lobbyists, not to Pennsylvanians.”

During Casey’s first two elections, he campaigned as a staunch supporter of the 2nd Amendment, and did not believe new gun control laws could stop mass shootings.

But a few weeks after he was re-elected in 2012, a gunman opened fire at Sandy Hook Elementary School in Newtown, Conn., killing 20 children and six adults. Casey told the Washington Post last year that his wife and daughters confronted him about his views on gun control, and Casey eventually changed his mind.

Casey has backed major gun control proposals since then. He introduced his own bill following the shooting at the Pulse Nightclub in Orlando last year that would have barred those convicted of hate crimes from buying guns. 

“Senator Casey does not believe that Americans should accept that regular mass shootings are the new normal,” said Max Steele, a spokesman for Casey’s campaign. “He’s taking on the gun lobby because he, like the vast majority of citizens in Pennsylvania and across the country, believes we should do everything we can to prevent these tragedies from tearing families and communities apart.”

Casey’s Keystone State colleague, GOP Sen. Patrick J. Toomey, has also been earned praise from gun control advocates. After the Newtown attack, Toomey teamed up with Democratic Sen. Joe Manchin III of West Virginia on a bill expanding background checks. The bill failed to move forward in the Senate. 

Casey was one of 22 Democrats to sign onto Sen. Dianne Feinstein’s bill banning more than 200 military style assault weapons. More than 2,000 guns would be exempt from the ban. 

But Casey was the only Democrat in that group who is running for re-election in a state that President Donald Trump won last year. Trump won Pennsylvania by less than one point. Nine other Democrats are running in states that Trump won.