Updated: 11:07 p.m.

Democrat Mark Critz won a special election Tuesday in southwestern Pennsylvania, a symbolic and consequential victory that will buoy the spirits of a party that is defending dozens of competitive districts in this fall’s midterm elections.

With 70 percent of precincts reporting, Critz led businessman Tim Burns by 53 percent to 45 percent and Burns conceded the election.

Critz will succeed his former boss, the late Democratic Rep. John Murtha, whose death in February necessitated Tuesday’s vote.

Critz emphasized a platform of job creation and said he would be an independent voice for Western Pennsylvania. Burns worked to nationalize the election by running as an opponent of the new health care law and other priorities of President Barack Obama and Speaker Nancy Pelosi (D-Calif.).

The Democratic Congressional Campaign Committee and the National Republican Congressional Committee each spent about $1 million on independent expenditures to influence the outcome, joining other groups outside the district that also invested in the race.

Democrats promoted Critz’s victory as a body blow to the Republican campaign to win a majority of House seats, noting that Pennsylvania’s 12th voted narrowly for Sen. John McCain (R-Ariz.) in the 2008 presidential election and that Republicans would have a hard time gaining dozens of seats if they couldn’t win Murtha’s seat.

“For all of their bluster about building a national wave this year, including RNC Chairman Michael Steele’s guarantee of victory for Tim Burns, Republican policies were once again rejected when it came time to face the voters,” DCCC Chairman Chris Van Hollen (Md.) said in a statement.

NRCC Chairman Pete Sessions (Texas) said the special election loss was “undoubtedly disappointing,” but he said the committee would take the lessons learned and move forward.

“The bottom line is that the makeup of the House remains the same and our goal of winning back the majority in November has not changed,” Sessions said in a statement. “In just four days, we will have another election in another Democrat-held seat that stands to change the makeup of the House.”

Republicans said that Gov. Ed Rendell (D) scheduled the special election to coincide with the statewide primary election, with the expectation that Democratic voters who turned out to choose nominees for governor and Senator would boost the party’s prospects in the 12th.

Burns and Critz won their respective primaries and will square off again in the November general election.

Upon Critz’s swearing-in, the House will have 255 Democrats and 177 Republicans, with vacancies in Democratic-held districts in Hawaii and New York and in a Republican-held district in Georgia.

Republicans are favored to win the Hawaii district in a special election Saturday that includes Republican Charles Djou as well as Democrats Ed Case and Colleen Hanabusa, who are dividing the Democratic vote.