Updated at 7:26 p.m. PT:
Two years after reclaiming control of Congress’ lower chamber, Republicans on Tuesday were holding onto their hefty majority in the U.S. House, NBC News projected.
Entering Tuesday’s elections, Republicans held a 240-190 advantage (five House seats are vacant -- two formerly GOP-held and three Democratic seats). By 10 p.m. ET, polls had closed in most states, and NBC News projected that Republicans would win enough seats to comfortably hang on to their majority.
“The American people want solutions, and tonight they responded by renewing our House Republican majority,” declared House Speaker John Boehner of Ohio, who ran unopposed in his re-election bid. "With this vote, the American people have also made clear that there’s no mandate for raising tax rates. What Americans want are solutions that will ease the burdens on small businesses, bring jobs home and let our economy grow."
“Just as in 2010, our House Republican candidates listened to the American people and rejected the Democrats' tax-and-spend agenda that threatens the American Dream,” added Rep. Pete
Sessions, R-Texas, chairman of the National Republican Congressional Committee.
In Wisconsin, Rep. Paul Ryan, GOP presidential candidate Mitt Romney’s running mate, was projected by NBC News to win re-election to his District 1 seat .
In the Senate, Republicans lost three races that they had targeted as critical to their hopes of winning control , making it appear increasingly likely that the next president would be dealing with a still-divided Congress.
Among the House races that were being closely watched either because they were in bellwether districts or because the candidates had instant name recognition:
6th District: Former GOP presidential candidate Rep. Michelle Bachmann is up for re-election against Democratic hotel businessman Jim Graves. In her fundraising emails, Bachmann has called the campaign the toughest of her life. With 8 percent of the votes counted, Bachmann had 53 percent to Graves' 47 percent. See results 
18th District: Freshman Republican Rep. Allen West, a former Army lieutenant colonel and prominent face of the tea party, faces Democrat Patrick Murphy, a 29-year-old construction executive and political neophyte. West has garnered headlines for insisting President Barack Obama is a Muslim and charging that scores of congressional Democrats are communists. It figured to be one of the most expensive House races in history: The two sides had raised nearly $21 million as of Oct. 17, according to the nonpartisan Center for Responsive Politics, and super PACs supporting the candidates poured in millions more. With 92 percent of the votes counted, each candidate had 50 percent. See results 
12th District: Rep. Mark Critz, a Democrat, won this western Pennsylvania seat in a May 2010 special election after the death of longtime Democratic Congressman John Murtha, for whom Critz worked. Critz survived the 2010 midterms, but faces a stiff challenge from attorney newcomer Keith Rothfus after a GOP-led redistricting. With 46 percent of the votes counted, each candidate had 50 percent. See results 
4th District: This race features five-term incumbent and outspoken conservative Republican stalwart Rep. Steve King and Democrat Christie Vilsack, wife of former Iowa governor and current U.S. Agriculture Secretary Tom Vilsack. King had never faced a serious challenge in the heavily Republican area, but the post-Census addition of Ames made the district less conservative. See results 
36th District: GOP Rep. Mary Bono Mack sought to stave off a challenge from emergency room physician Raul Ruiz in the newly redistricted 36th. Bono Mack has held the seat since 1998, when she won a special election to replace her late husband, Sonny Bono, half of the singing duo Sonny and Cher. Sonny Bono was killed in a 1998 skiing accident in South Lake Tahoe. After redistricting, registered Democrats now outnumber Republican voters in the 36th -- making this the first time Bono Mack will seek re-election in a blue district. Bono Mack’s husband, Rep. Connie Mack, R-Fla., was projected to lose his Senate race in Florida to favored Democratic Sen. Bill Nelson. See results 
Behind the numbers
Republicans, running on a promise to shrink government and roll back unpopular federal policies and proposals, took control of the U.S. House of Representatives in 2010, winning a whopping 63 seats in the midterm elections. Republicans said the landslide victory was a referendum on Obama's and the then-incumbent party's performance.
The 2012 elections will be the first using new redistricting maps drawn up after the 2010 Census. Every 10 years, states redraw their congressional-seat boundaries, and redistricting favored Republicans in many areas this time around. Some moderate Democrats decided to retire rather than seek re-election in Republican-leaning districts.
“Democrats couldn't have picked a worse year to suffer horrific losses up and down the ballot than 2010,” wrote David Wasserman in the Cook Political Report. “In effect, the GOP won the right to draw much of the political map for the next 10 years."