A congressional leadership PAC tied to Speaker Paul Ryan says its pro-second amendment ad about Democrat Conor Lamb helped Republican Rick Saccone in the race that may end up going to Democrat Lamb by a hair’s margin.

Lamb held a 627-vote lead over Republican Rick Saccone in the Pennsylvania 18th congressional district special election as of Monday afternoon, according to the Pennsylvania Department of State unofficial ballot count in the March 13 special election. That’s approximately one-quarter of one percent.

The first television ad that Lamb ran touted his time in the Marines and that he “still loved to shoot,” according to the Washington Post. After the school shooting in Parkland, Florida, Lamb walked a line between support for stricter background checks and hesitation about new gun laws.

Just one week later, the Congressional Leadership Fund sent some Democrat voters in Allegheny County ads painting Lamb as “supporting our second amendment rights” and “opposing gun restrictions.”

The Post report didn’t detail the full reach of the ad. A spokeswoman with CLF told Breitbart News that “These mailers went to 12,000 anti-gun Democratic women who were 90% less likely to support Conor Lamb after hearing his views on gun restrictions.”

The mailer was message tested before distribution and claims that it definitely cost Lamb votes, according to the PAC. The PAC also maintains that it was the first to go into the PA-18 race and spent over three and a half million dollars there.

“Our job was to make sure voters in Pennsylvania knew where Lamb stood on important issues and that’s why this mailer was sent to those who would find his second amendment stances of note,” CLF spokeswoman Courtney Alexander told Breitbart News on Friday.

Many locally elected Democrats in the district oppose abortion and gun control, according to the Post. While there are more registered Democrats than Republicans, President Donald Trump won the district in 2016 by 19 points.

Due to redistricting, whoever ultimately comes out victorious in the PA-18 race will not run for re-election, but would have to run again in a different district.

Follow Michelle Moons on Twitter @MichelleDiana