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(CNN) -- Riding a wave of voter discontent, Republicans picked up six Senate seats Tuesday but fell short in their bid to wrest control of the upper house from Democrats and oust Senate Majority Leader Harry Reid, CNN projected, based on its analysis of exit poll data.
The results mean that Congress will be divided. Republicans are projected by CNN to win control of the House of Representatives for the first time in four years. With a Democratic in the White House, the risk of legislative gridlock looms large.
Republicans flipped six Senate seats -- in Pennsylvania, Illinois, Indiana, Arkansas, North Dakota and Wisconsin, CNN predicts -- a significant gain, but less than the 10 seats they needed to win the much-coveted 51-seat Senate majority.
Democrats similarly won several key races, CNN predicts, including Delaware, Connecticut, West Virginia and California.
Reid also is projected to win in Nevada, a major victory for Democrats. He defeated Tea Party favorite Sharron Angle, a former state legislator, who beat 11 other opponents in the crowded June primary to clinch the GOP nomination, CNN predicts.
A cheering crowd of supporters chanted Reid's name and "si se puede" -- Spanish for "yes we can" -- Tuesday night. Reid thanked them for their help securing his win.
"I've been in some pretty tough fights in my day ... But I have to admit, this has been one of the toughest," he said.
Going into the election, Democrats controlled 59 Senate seats, including 2 independent senators. Republicans controlled 41. At stake in the elections were 37 seats in the Senate.
Republicans performed well overall, speaking to voters' anger and anxiety over the economy. A political newcomer, the Tea Party, also made its a strong showing Tuesday, backing two GOP Senate winners.
"There's an earthquake election going on all over this country," said incumbent Republican Sen. Jim DeMint, who CNN projects won his bid for re-election to a second term in South Carolina. "People have realized that the future is in their hands, not in that of politicians."
Republican Dan Coats bested Democratic Rep. Brad Ellsworth to win Indiana's Senate race, CNN projects, handing the GOP its first Senate seat gain of the night.
Republican Rep. John Boozman defeated Democratic incumbent Sen. Blanche Lincoln, CNN projects in Arkansas, giving the GOP a second Senate seat. Republican Gov. John Hoeven won North Dakota's Senate race, CNN projects, for the third seat. Republican businessman Ron Johnson defeated Democratic incumbent Russ Feingold, CNN projects, for the fourth flip.
Republican candidate Pat Toomey defeated Democratic Rep. Joe Sestak to win the Pennsylvania Senate seat, CNN projects, for the fifth Republican Senate seat gain. And Republican Rep. Mark Kirk won the Illinois Senate race, CNN projects, defeating Democratic nominee Alexi Giannoulias for President Barack Obama's seat in the sixth flip of the night. Democratic Sen. Roland Burris, who replaced Obama, is retiring.
"It was a vote for fiscal responsibility, for spending restraint, for lower taxes, for bringing down the deficit. A vote to put our economy back to work," Kirk said to cheers from the crowd.
In Delaware, Democrat Chris Coons defeated Tea Party-backed Republican nominee Christine O'Donnell, who won nationwide attention when she clinched the GOP nomination, CNN projects.
In Florida, Republican Marco Rubio, similarly supported by the Tea Party, won the Senate seat vacated by retiring Republican Sen. George LeMieux, CNN projects.
Democratic West Virginia Gov. Joe Manchin won his state's Senate seat, CNN projects, defeating Republican nominee John Raese in a tight race for the late Sen. Robert Byrd's seat. Manchin promised to work with Republicans.
"Tomorrow starts the rebuilding of America," said Manchin, who also paid tribute to Byrd.
Democrat Richard Blumenthal took the Connecticut Senate seat left open by retiring Democratic Sen. Chris Dodd, CNN projects, defeating Republican nominee Linda McMahon, a wealthy former professional wrestling executive. Blumenthal vowed to fight for senior citizens and the middle class.
Democratic incumbent Sen. Barbara Boxer won a fourth term in the Senate, CNN projects, defeating GOP nominee Carly Fiorina, the former CEO of Hewlett-Packard and adviser to John McCain's presidential campaign in 2008.
Republican candidate and Tea Party favorite Rand Paul won the Kentucky Senate race, CNN projects, beating out Democrat Jack Conway.
"We have come to take our government back," said Paul, soon after being projected the winner. "America will remain great if and when we understand that government cannot create prosperity."
CNN's Catherine E. Shoichet contributed to this report.