Merged district

Iowa was one of 10 states to lose seats in Congress because of redistricting, setting up a member-on-member showdown between two veteran lawmakers in a merged Des Moines-area district. Democrat Leonard Boswell represented much of this new district in the late 1990s. Republican Tom Latham had a fundraising advantage due in part to his friendship with Boehner. The cash advantage was apparent on the airwaves, where Latham outspent Boswell, even when counting the considerable assistance the Democrat received from his national party. Boswell is no stranger to tight races. He survived the Republican wave of 2010.

Iowa 4: Rep. Steve King (R) vs. Christie Vilsack (D)

Republican incumbent Steve King's bid for a sixth term in Congress was his toughest. King won re-election in his old western Iowa district with 66% of the vote in 2010, and he never dipped below 59% in any of his previous races. This year, he faced a new district and a tough new challenger in Democrat Christie Vilsack, Iowa's former first lady and the wife of U.S. Agriculture Secretary Tom Vilsack. The good news for King was that his enormous new district in the northwest part of the state comprises mostly counties won in 2008 by John McCain. King had a fundraising advantage over Vilsack. But Vilsack was the strongest candidate Democrats could have fielded.

Louisiana 3: Rep. Charles Boustany (R) vs. Rep. Jeff Landry (R)

Merged district

As in California, redistricting and a "top-two" primary system forced two incumbent lawmakers of the same party into a November showdown. Republican Charles Boustany, a surgeon elected in 2004, faced freshman Republican Jeff Landry, an attorney and businessman, former police officer and tea party favorite. Boustany represented more of the new district than did Landry, but the freshman proved he was capable of pulling off surprises when he defeated the better-known former Louisiana House speaker in the 2010 primary. Under state law, the November election serves as an open primary, in which the top two finishers will advance to a December runoff if no one gets a majority.

Maryland 6: Rep. Roscoe Bartlett (R) vs. John Delaney (D)

Republican Roscoe Bartlett's bid for an 11th term appears to have been his last. The long-time western Maryland representative was a target for Democrats who redrew the district last year. As a result, his once-safe seat now stretches from the state's westernmost point to include a piece of heavily Democratic Montgomery County and now reaches almost to the District of Columbia border. His Democratic opponent was John Delaney, a wealthy businessman. Delaney pulled off an upset in the Democratic primary over Rob Garagiola, a state senator with a string of endorsements from party establishment types, including Gov. Martin O'Malley. Bartlett had little hope of pulling off a miracle.

Massachusetts 4: Joe Kennedy III (D) vs. Sean Bielat (R)

Open Democratic-held seat

After a two-year absence, the famed Kennedy family once again has an elected representative in national politics.

Joe Kennedy III will serve Massachusetts' 4th district, having handily defeated GOP opponent Sean Bielat, according to a CNN projection. The seat became open when longtime Democratic Rep. Barney Frank, who has been a leading proponent of financial regulations, announced this year that he was retiring.

Kennedy is the 32-year-old grandson of slain Sen. Robert Kennedy of New York. His great-uncles are the late President John F. Kennedy and long-time Sen. Ted Kennedy, D-Massachusetts, who died in office in 2009.

Democratic Rep. Patrick Kennedy of Rhode Island left office in January 2011, ending his family's 64-year streak of service in the U.S. Congress.

Joe Kennedy is a former prosecutor and Peace Corps member; Bielat is a businessman and Marine Corps reservist.

Massachusetts 6: Rep. John Tierney (D) vs. Richard Tisei (R)

Rep. John Tierney was in danger of becoming the first Democrat since 1994 to lose a U.S. House race in Massachusetts. The eight-term incumbent was dogged by a financial scandal involving his wife and her brothers and an illegal gambling operation. The Republican nominee was Richard Tisei, a former state senator who is openly gay. Tierney was targeted by more than $3 million in ads this cycle from Tisei, the national Republican Party and pro-Republican groups, eager to defeat a Democrat in Massachusetts. The district is Democratic but the ongoing scandal appeared to have taken a toll. A September Boston Globe/University of New Hampshire poll had Tisei with 37%, Tierney with 30% and 30% undecided.

Minnesota 6: Rep. Michele Bachmann (R) vs. Jim Graves (D)

Tea party favorite Michele Bachmann was a shoo-in for re-election when she folded up her presidential campaign in January. Ten months later, Bachmann still had the advantage but she faced a tough challenger in Jim Graves, a wealthy businessman. Graves waged a competitive race in October, spending $1.2 million in TV ads, compared with $1.7 million for Bachmann. The conservative congresswoman had never posted huge numbers on Election Night, but redistricting made her district slightly more Republican. Nevada 4: Steven Horsford (D) vs. Danny Tarkanian (R)

New district

There was a competitive race in Nevada's newest congressional district. The nominees were Democrat Steven Horsford, the state senate majority leader, and Republican Danny Tarkanian, a businessman and son of UNLV basketball coaching legend Jerry Tarkanian. The younger Tarkanian was a 2010 U.S. Senate candidate, but placed third in the Republican primary. The two candidates had been evenly matched in terms of fundraising as well as assistance from their national parties and from outside groups in terms of TV ads. The district leans slightly Democratic.

New Hampshire 1: Rep. Frank Guinta (R) vs. Former Rep. Carol Shea-Porter (D)

As was the case in 2010, Republican Frank Guinta and Democrat Carol Shea-Porter faced off in the battle for New Hampshire's 1st Congressional District. This time, Guinta was the incumbent and Shea-Porter the challenger. Shea-Porter was elected in the Democratic wave of 2006 and served two terms before losing to Guinta in 2010, 54%-42%. The two were fairly evenly matched in fundraising.

New Hampshire 2: Rep. Charlie Bass (R) vs. Ann McLane Kuster (D)