Updated 7:30 p.m. | A new poll released today by the campaign of Rep. Mark Critz (D) showed him in a tightening primary with frontrunner Rep. Jason Altmire (D) in Pennsylvania’s newly reconfigured 12th district. The poll coincided with the Pennsylvania AFL-CIO’s endorsement of Critz today.

“We’re proud to endorse Congressman Critz in the 12th Congressional District.  He’s the best candidate to represent the over 100,000 union members in CD12 who are looking for someone to fight for jobs and an economy that works for everyone,” Pennsylvania AFL-CIO President Richard Bloomingdale said in a statement to Roll Call.

A Democratic operative familiar with the race said by endorsing, the labor group is asserting independence and a willingness to wade into Democratic primary fights. The source also said the race is a dry run for the AFL-CIO’s post-Citizens United campaign operation. Beyond endorsing, an AFL-CIO official said the group would be putting resources into campaigning for Critz.

Altmire, who declined to comment, angered liberals with his vote against President Barack Obama’s health care law in 2010.

He led Critz by 7 points in the poll of likely Democratic primary voters by Global Strategy Group. The poll was taken March 22-25 and had a margin of error of 4.9 points. In a horserace matchup, Critz took 38 percent to Altmire’s 45 percent.

A Critz poll last month had shown Altmire with a 10-point lead. The primary is April 24.

“There’s still plenty of campaign left,” Critz spokesman Mike Mikus told Roll Call, “and it’s moving in the right direction.”