A second super PAC has jumped into the highly competitive race for Pennsylvania's Fifth Congressional District.

The group, known as "Progress in PA-05," is backing Democrat Ashley Lunkenheimer. Depending on how much the super PAC spends, it could be a major boost for her campaign.

Lunkenheimer, a former assistant U.S. attorney, is seen as one of the leading candidates in the 10-person Democratic primary for the seat in the Philadelphia suburbs. She received the second-highest number of votes in an endorsement meeting held recently by the Delaware County Democratic Party.

Only one other candidate in the primary, former deputy mayor Rich Lazer, is known to have the support of a super PAC. That committee was launched by John "Johnny Doc" Dougherty, the powerful leader of Philadelphia's electricians union, and is spending $200,000 on TV ads over the next week.

It is unclear who is funding the super PAC for Lunkenheimer. The committee has not disclosed any donations. Its treasurer, Brian Lenzmeier, did not respond to repeated requests for comment.

The super PAC lists its address as a suite in a high-rise building in Washington where the political law firm Sandler Reiff Lamb Rosenstein & Birkenstock is located. A woman who answered the phone at the company said Progress in PA-05 is one of its clients.

Progress in PA-05 has spent more than $18,000 for mailings in support of Lunkenheimer, according to records filed this week with the Federal Election Commission. The group submitted a statement of organization earlier this month.

Super PACs can spend an unlimited amount of money on elections as long as they don't coordinate with political campaigns. A spokesman for Lunkenheimer declined to provide comment.