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)

Republican incumbent Charlie Bass faced Ann McLane Kuster. Kuster lost to Bass in the general election in 2010 but ran again, and outraised Bass, though they started October with roughly the same amount in the bank. The Democrat far outspent her opponent on the airwaves even though the national Republican Party invested funds on behalf of Bass.

New York 24: Rep. Ann Marie Buerkle (R) vs. Former Rep. Dan Maffei (D)

Rep. Ann Marie Buerkle was elected in the Republican wave of 2010 and had to defend her seat Tuesday from the man she defeated. Democrat Dan Maffei, a longtime Capitol Hill staffer, won this upstate New York district in 2008 after it had been in Republican hands for almost 30 years. He lost the seat to nurse and tea party favorite Buerkle in one of the closest House races that year. The two had been evenly matched in fundraising and TV ad spending. The district leans slight more Democratic.

North Carolina 7: Rep. Mike McIntyre (D) vs. David Rouzer (R)

Democratic Mike McIntyre ran a competitive race despite a newly redrawn district that skews heavily Republican. The Republican nominee was David Rouzer, a state senator. McIntyre, an eight-term incumbent, led in fundraising and kept even with ad spending by pro-Republican outside groups and the national Republican Party. Rouzer stayed off the airwaves. Like fellow southern Democrat John Barrow in Georgia, McIntyre showed strong signs of life in a district that appeared to have been drawn to end his career.

Ohio 9: Rep. Marcy Kaptur (D) vs. Samuel "Joe the Plumber" Wurzelbacher (R)

Samuel Wurzelbacher, better known as "Joe the Plumber," became a conservative icon in the 2008 presidential race when he challenged then-candidate Obama on tax policy at a campaign event. Republican John McCain even mentioned him during the third presidential debate. Four years later, Wurzelbacher was running for Congress in a quixotic race against 15-term incumbent Democrat Marcy Kaptur, who was a safe bet for re-election. Kaptur handily defeated fellow Democrat Dennis Kucinich in a primary earlier this year.

Ohio 16: Rep. Jim Renacci (R) vs. Rep. Betty Sutton (D)

Ohio's most competitive House race pitted freshman Republican incumbent Jim Renacci against three-term Democratic incumbent Betty Sutton. Since August, the two had benefited from about $2 million in ad spending on their behalf from parties and outside groups, while Renacci's campaign about doubled Sutton's campaign in ad spending. The merged district, located in northeastern Ohio near, but not including, Cleveland, Akron, and Canton, leaned Republican but the race was up for grabs.

Tennessee 4: Rep. Scott DesJarlais (R) vs. Eric Stewart (D)

Republican physician Scott DesJarlais was elected to Congress in the Republican wave of 2010, defeating Democratic Rep. Lincoln Davis. He was a safe bet for re-election until a recent revelation that he had pressured a girlfriend to have an abortion a decade ago. DesJarlais was separated from his wife at the time. The Democratic nominee was Eric Stewart, a state senator. He had begun making an issue of the incident but the impact on DesJarlais' campaign in this rural, conservative district was unclear.

Texas 23: Rep. Francisco Canseco (R) vs. Pete Gallego (D)

Republican Francisco "Quico" Canseco was one of many freshman members elected in the GOP wave of 2010 who found himself in a competitive race for a second term. Canseco was a wealthy commercial real estate developer when he won his third bid for this seat two years ago, defeating Democratic incumbent Ciro Rodriguez. After a legal battle over the redistricting process, Canseco ended up with a district slightly more Democratic -- President Obama carried it in 2008 with 51%, according to the Cook Political Report. The Democratic nominee was Pete Gallego, a state representative who defeated former Rep. Rodriguez in the primary. Hispanics make up 66% of voters.

Utah 4: Rep. Jim Matheson (D) vs. Mia Love (R)

As Utah's only Democratic member of Congress, Jim Matheson was used to close races. He barely squeaked by in 2010 with 50% of the vote. This year may have proved to be Matheson's toughest race yet. His Republican opponent was Mia Love, the mayor of Saratoga Springs who would become the first female African-American Republican to serve in Congress. Love is a rising star in the party and was given a prominent speaking role at this year's Republican National Convention. The two were evenly matched in fundraising.

Wisconsin 1: Rep. Paul Ryan (R) vs. Rob Zerban (D)

Being named Mitt Romney's vice presidential running mate did not affect Paul Ryan's chances at getting re-elected to the House. He was a safe bet for against Kenosha County Supervisor Rob Zerban.

Ryan was asked multiple times whether he was hedging his bets by running for re-election while also running for vice president, but the question was irrelevant. Ryan was tapped for the ticket after the deadline had passed to have his name removed from the House ballot. Vice President Joe Biden was in the same position in 2008.

Wisconsin 7: Rep. Sean Duffy (R) vs. Pat Kreitlow (D)

Rep. Sean Duffy was one of the higher-profile freshmen elected in the Republican wave of 2010. He was a former Ashland County district attorney and tea party favorite, but he was probably best known for his work as a professional lumberjack athlete and ESPN commentator and as a cast member on MTV's reality show "The Real World." This year he faced a tough challenge from Pat Kreitlow, a former state senator and former local TV news anchor. Redistricting gave Duffy a more-GOP-leaning district. He also enjoyed a financial advantage. Despite these advantages, this remained the most competitive House race in Wisconsin.