(CNN) - Two hard-hitting new ads are heating up the Pennsylvania battle for the late Rep. Jack Murtha's congressional seat.
Republican Tim Burns is facing off against Democrat Mark Critz in a the May 18 special election. The race has stepped up in intensity in recent weeks, with both campaigns as well as national party committees going up with television ads.
The Burns campaign came out Tuesday with a new television commercial that questions the ethics of Critz, a longtime aide to Murtha, a Democrat who represented the district for 18 terms until he passed away earlier this year.
"Mark Critz. A Washington bureaucrat bankrolled by Pelosi. Critz was investigated by the congressional ethics office and Critz was in charge of the finances for a company caught on paying their taxes," says the narrator in the ad.
"The Ethics Committee found that Mr. Murtha did nothing wrong. Tim Burns knows this," Critz told CNN, responding to Burns' ad. "I worked for Parkins, a local small business, because I wanted to try to help my brother-in-law's company turn around its operations so that it could bring jobs to our community. I left because I disagreed with decisions that were being made over the company's future. These misleading personal attacks are Tim Burns' attempt to distract from his own record on job loss and outsourcing."
Meanwhile, the Democratic Congressional Campaign Committee is up with a new ad that goes after Burns.
"Millionaire Tim Burns sold his company, sold it to a corporation that used a tax loophole which encourages sending American jobs overseas. Burns got rich even though he knew there may be layoffs in Pittsburgh," says the narrator.
"The new DCCC ad is more false, negative attacks from the Pelosi attack machine in Washington. Tim Burns started TechRx in the basement of his home and grew it to over 400 new jobs," said Burns spokesman Kent Gates. "TechRx was sold to NDCHealth with the goal of expanding operations and increasing employment. NDCHealth was never Tim Burns' company though he did remain for a brief period during the transition of the sale. NDCHealth followed existing laws to maximize revenues for job creation."
Pennsylvania's 12th congressional district, which stretches from Cambria County in west-central Pennsylvania down to the southwestern corner of the state, is considered socially conservative. In the 2004 presidential election, Sen. John Kerry, D-Massachusetts, won the district by 2 points. Sen. John McCain, R-Arizona, narrowly edged out then Sen. Barack Obama, D-Illinois, in the district in 2008, even though Obama carried the state by 10 percent.
Charlie Cook and Stuart Rothenberg, two well respected non-partisan political handicappers, both rate the race as a toss-up. The winner of next month's special election will have to defend the seat in November.
Updated 5:46 p.m. : Late Tuesday afternoon Cook moved the race to lean Republican.
Follow Paul Steinhauser on Twitter: @psteinhausercnn