By Greg Giroux, CQ Staff

The campaigns for the congressional primaries held Tuesday in Pennsylvania were overshadowed by the donnybrook Democratic presidential primary between Sens. Hillary Rodham Clinton and Barack Obama . But the consequences of those House nomination contests will be felt this fall in a state that will host some of the year’s most competitive races for Congress.

It is easy to figure why Pennsylvania is again a hotbed for House races as it was in 2006. Four of the 30 seats Democrats wrested from Republicans nationally in their successful drive for a House majority were in Pennsylvania, and the GOP is staging bids to recapture three of them that CQ Politics rates as competitive. But Democratic strategists, who are striving aggressively across the nation to expand upon their 2006 gains, are running takeover bids in four of the Pennsylvania districts that the Republicans still hold.

The most dispositive primary Tuesday was in the north-central 5th District, a Republican stronghold where six-term GOP Rep. John E. Peterson left the seat open to retire at the end of the current Congress. The likelihood of strong job security for the Republican nominee drew a crowded field in which Glenn Thompson, a health care professional and Republican activist, emerged on top. Although he received a plurality of just 19 percent of the Republican primary vote, his win installs him as the strong front-runner for the November contest to succeed Peterson.

• Republican challengers. Of the places where the Republicans are seeking to take back seats from freshman Democrats, their most vigorous challenge is likely to be in the 10th District. Businessman Chris Hackett narrowly won the Republican nomination in this mostly conservative swath of northeastern and east-central Pennsylvania, where he will oppose Democratic Rep. Christopher Carney .

In nearly complete returns, Hackett had 52 percent of the vote against another businessman, Dan Meuser, in a contest that saw hard-hitting attacks and substantial personal spending from both candidates. Hackett was backed by some conservative groups in Washington because of his support for a system of personal savings accounts under Social Security and his outright opposition to appropriations earmarks.

Carney, a political scientist and former Pentagon consultant, won the seat in 2006 over Republican Rep. Don Sherwood, who was badly damaged by a sex scandal. The Democrat is seeking re-election in a district where 60 percent of the voters backed President Bush in 2004. Only two districts taken over by Democrats in 2006 gave Bush a higher share of their votes two years earlier.

But Carney is well-funded, with $966,000 in his campaign account as of April 2, and probably won’t shy from pointing out differences between his record and that of the more liberal Democratic leadership.

The candidate matchups for the Republicans’ other key takeover bids in Pennsylvania were predetermined and simply confirmed by the primaries. In the western 4th District, Democratic Rep. Jason Altmire and Republican former Rep. Melissa A. Hart will compete in a rematch of their 2006 contest. Altmire, a health association executive, took 52 percent that year to quash Hart’s bid for a fourth term.

Freshman Democratic Rep. Patrick J. Murphy will be opposed by Republican Tom Manion, in the 8th District, which is dominated by Bucks County north of Philadelphia. It is a race in which both candidates are indelibly and personally linked to the ongoing Iraq War. Murphy, who unseated one-term Republican Rep. Michael G. Fitzpatrick in 2006, is the only Iraq War veteran in Congress. Manion is a retired Marine Corps colonel whose son died while serving in Iraq last year.

Republican strategists have been heavily promoting what appears a longshot bid against 12-term Democratic Rep. Paul E. Kanjorski by Lou Barletta, a local mayor and a vigorous opponent of illegal immigration, in the 11th District, which includes Scranton, Wilkes-Barre and other territory in northeastern Pennsylvania. The two men were opponents in 2002, when Kanjorski won by 14 percentage points, the closest race of his career.

Republican officials say Barletta will be a better candidate than he was six years ago, pointing to some nationwide attention he has received for his effort to curb illegal immigration in his community. Democratic officials note, though, that Barletta’s first-quarter fundraising was underwhelming. He raised $185,000 and had $154,000 remaining as of April 2, while Kanjorski had more than $1.8 million left in his campaign account after collecting $453,000 in this year’s first quarter.

• Democratic Takeover Targets. In two districts — the 3rd and the 18th — Democrats selected nominees in multi-candidate primaries to oppose Republican incumbents who faced meager Democratic opposition in 2006.

Businesswoman Kathy Dahlkemper will oppose seven-term Republican Rep. Phil English after topping a four-candidate Democratic field in the 3rd District, which takes in Erie and other territory in northwestern Pennsylvania. Dahlkemper, the director of the Lake Erie Arboretum, had 45 percent of the vote in a race that also included Kyle Foust (26 percent), an elected councilman in Erie County; Tom Myers, a lawyer (19 percent); and Mike Waltner (11 percent), a community outreach worker.