[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2010/images/02/17/art.murtha.file.gi.jpg caption="The contest for John Murtha's seat remains up in the air."](CNN) - Keep your eyes on southwestern Pennsylvania. While it's being overshadowed by higher-profile Senate primaries, a special election Tuesday for a House seat that represents that part of the state has drawn national attention and could have national implications.
And while the winners in the Senate primaries move onto the general election in November, the victor in this contest goes directly to Congress.
Republican Tim Burns is battling Democrat Mark Critz to fill the seat of the late Rep. John Murtha.
The race has stepped up in intensity over the past month, with both campaigns as well as national party committees going up with television ads.
Burns is a businessman and Critz was a longtime aide to Murtha, a fellow Democrat who represented the district for 18 terms until he passed away from complications following gallbladder surgery this year.
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.
Rothenberg said that Critz should have an advantage in the race "given the large Democratic registration advantage in the district and the district's strong support for the late Rep. John Murtha."
"A Burns victory would be a bad sign for Democrats for the fall," added Rothenberg, editor and publisher of the Rothenberg Political Report.
"In some ways, PA-12 seems to be a must-win for Republicans. After all, if they can't win the only district in the country that voted for both John Kerry and John McCain, what does it say about their ability to win other GOP-tilting seats this fall?" said Amy Walters, editor-in-chief of National Journal's The Hotline.
In a sign of just how much is at stake in this race, two high-profile surrogates parachuted into the district last weekend. Former President Clinton campaigned for Critz at a rally in Johnstown while Sen. Scott Brown of Massachusetts stumped for Burns in Washington, Pennsylvania.
Democratic and Republican officials agree on one thing: This contest will be close.
"This is going to come down to turnout." said National Republican Campaign Committee communications director Ken Spain.
"We expect this race to go right down to the wire," added Democratic Congressional Campaign Committee spokesman Ryan Rudominer.
The victor in this special election won't have long to celebrate. The winner will have to defend the seat in November.