Supporters cheer before Kansas Sen. Pat Roberts makes his victory speech during a Republican watch party Tuesday, Nov. 4, 2014, in Topeka, Kan. Bow Stanley, from Silver Lake, Kan, votes at the Prairie Home Cemetery building, Tuesday, Nov. 4, 2014, in Topeka, Kan. WASHINGTON (AP) - Republicans rolled in a series of races Tuesday to seize control of the Senate, the biggest prize in the midterm elections. This, while seeing two vulnerable GOP governors defeat their challengers in marquee races in Wisconsin and Florida and building an even stronger majority in the House. Altogether, Republicans needed to gain six seats to win back the Senate majority they lost in 2006. They achieved that and much more. In West Virginia, South Dakota and Montana, Republicans switched open seats that had been held by Democrats to their column. Then they added Arkansas, where incumbent Democrat Mark Pryor lost a closely fought race to Republican Tom Cotton. Colorado made it five pickups, as Democratic incumbent Mark Udall lost to Rep. Cory Gardner. Meanwhile, Democrats' push for a turnover in Kentucky failed when GOP Sen. Mitch McConnell won re-election in his closely watched race. And their hopes of seeing an independent defeat Sen. Pat Roberts in Kansas - one possible path to keeping Democrats in charge of the Senate - came to nothing. Then came North Carolina, the most expensive Senate race in the nation. Republican Thom Tillis beat Democratic incumbent Sen. Kay Hagan to clinch Senate control for the GOP. Iowa made it a gain of seven seats as Republican Joni Ernst beat Democrat Bruce Braley. Democrats entered the night with a 53-45 Senate majority, plus two independents who usually have supported them. Outstanding races, Alaska and Louisiana among them, held further possibilities for the GOP. They failed in New Hampshire, where Democrat Jeanne Shaheen held off a high-profile challenge from Republican Scott Brown. Democrats had hoped to see Republicans defeated in Georgia as well as Kansas but the GOP held on. Republicans won a commanding majority, pushing their dominance to near-historic levels. They defeated some of the last white Democrats in the South and penetrated Democratic strongholds nationwide. The GOP, going into the election with a 234-201 majority, was on track to match or surpass the seats it held during Democratic President Harry Truman's administration more than 60 years ago. They gained 14 seats and counting; Democrats just one. Republicans claimed three Democratic seats in New York, upending six-term Rep. Tim Bishop on Long Island and Dan Maffei in the Syracuse area while winning an open seat upstate. The results were a blow to Rep. Steve Israel, D-N.Y., chairman of the Democratic Congressional Campaign Committee. The GOP defended 22 governor's seats, Democrats 14. Half a dozen Republican governors who swept into office in 2010, some with tea party support, faced fierce challenges in the campaign. GOP Gov. Sam Brownback survived by a slim margin in solidly Republican Kansas. Wisconsin Gov. Scott Walker, on the ballot for the third time in four years, defeated Democratic challenger Mary Burke. That cleared a huge hurdle for Walker as he prepares for a possible run for the Republican presidential nomination in 2016. Democrats and their labor allies had salivated at the prospect of defeating the governor who effectively ended collective bargaining for most public workers in the state after his election in 2010. In Florida, GOP Gov. Rick Scott also held onto office in the nation's biggest swing state despite a strong challenge from Democrat Charlie Crist, a former GOP governor who changed parties to run for his old job. But in Pennsylvania, GOP Gov. Tom Corbett fell to Democrat Tom Wolf. Voters experienced sporadic glitches but there were no immediate signs of anything serious enough to affect the outcome of an election. Virginia officials reported problems with 32 machines that prevented voters from immediately casting accurate ballots. A Georgia website designed to help voters locate polling places instead directed many users to an error message. A Connecticut judge ordered two polling places in Hartford to stay open a half-hour late. Crist's campaign for Florida governor filed a motion to extend voting by two hours in Broward County. It was denied. Nearly 150 ballot measures were decided Tuesday. Oregon and the District of Columbia legalized the use of recreational pot. In Colorado and North Dakota, voters rejected measures that opponents feared could lead to bans on abortion, while Tennessee voters approved a measure that will give state legislators more power to regulate abortion. Voters in four states approved minimum wage increases. Associated Press writers Kimberly Hefling, Nedra Pickler, Eric Tucker and Ken Thomas contributed to this story.