(CNN) -- Democrats have narrowly clung to their Senate majority, staving off Republican wins in several key states, CNN projected, based on its analysis of exit poll data.
Republicans made significant headway in Tuesday's elections, riding a wave of voter discontent to gain at least six Senate seats. But they fell short in their bid to oust Senate Majority Leader Harry Reid, CNN projected.
The GOP flipped seats in Pennsylvania, Illinois, Indiana, Arkansas, North Dakota and Wisconsin, CNN predicts -- a significant gain but fewer than the 10 seats they needed to win the much-coveted 51-seat Senate majority.
On Wednesday, as President Barack Obama acknowledged that Democrats suffered a "shellacking," there was some good news out of the Rocky Mountains for the party.
Democratic incumbent Sen. Michael Bennet has won a tight battle with Republican challenger Ken Buck to retain his seat in Colorado, CNN projects. The victory gives Democrats 52 members in the Senate, with races in Washington and Alaska remaining too close to call Wednesday.
Both campaigns were predicting victory once every vote is counted, but attorneys from both sides were bracing themselves for a possible recount.
The projection of Reid's win in Nevada is 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. The former boxer thanked them for their help securing his re-election.
"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.
On Wednesday, however, Reid said it is time for the Senate to promote bipartisanship.
"I think what we need to do is stop using words like 'chastened,' and I think what we have to do is recognize that all of us, all of us, who are going to be in the Senate have to work together," he said.
"That's the message from the American people. We must work together, and I'm looking forward to that. I have a good relationship with Mitch McConnell, my Republican counterpart. I've known John Boehner for many years. I think this is a time we need to set aside our speeches and start rolling up our sleeves and have a little sweat on our brow," Reid said.
Going into the election, Democrats controlled 59 Senate seats, including two independent senators. Republicans controlled 41. At stake were 37 seats in the Senate.
Whatever the final makeup of the Senate, it will include no African-American members. Roland Burris, the only current African-American senator, is retiring. None of the three African-American candidates -- Democrats Kendrick Meek, Alvin Greene and Mike Thurmond -- won Tuesday, according to CNN projections.
Only six black senators have ever served in the U.S. Senate: three Republicans and three Democrats, including Barack Obama.
Republicans had a strong showing overall in Tuesday's election, speaking to voters' anger and anxiety over the economy. A political newcomer, the Tea Party, also made its mark 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."
In a tight battle and a significant win for Tea Party activists, Republican candidate Pat Toomey defeated Democratic Rep. Joe Sestak to win the Pennsylvania Senate seat, CNN projects. Tea Party-backed Republicans Ron Johnson in Wisconsin, Mike Lee in Utah and Marco Rubio in Florida also won Senate seats, CNN projects.
Rand Paul, another Republican candidate and Tea Party favorite, won the Kentucky Senate race, CNN projects, beating out Democrat Jack Conway.
"We have come to take our government back," Paul said soon after being projected the winner. "America will remain great if and when we understand that government cannot create prosperity."
On Wednesday, Reid defended the health care reform bill passed this year.
"The health care bill is very important," he told CNN. "I wish the Republicans had worked with us when we did the health care bill. If there's tweaking we need to do with the health care bill, I'm ready for some tweaking, but I'm not going to in any way denigrate the great work we did as a country in saving Americans from bankruptcy because of the insurance industry bankrupting us."
In Illinois, Republican Rep. Mark Kirk scored a major symbolic victory when he defeated Democratic nominee Alexi Giannoulias for Obama's former seat. Burris, a Democrat who replaced Obama, is retiring.
"Tonight the sun set on a one-party, corrupt state. And this Senate seat was just returned to its rightful owners, the people of Illinois," Kirk told supporters Tuesday night.
But Democrats won several key races, CNN predicts, including Delaware, Connecticut, West Virginia and California.
In Delaware, CNN projects that Democrat Chris Coons defeated Tea Party-backed Republican nominee Christine O'Donnell, who won nationwide attention when she clinched the GOP nomination.
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," he said, also paying 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.
"After the toughest and roughest campaign of my life, this is my eleventh straight election victory, and what a sweet one it is," Boxer said.
CNN projections have indicated that one of the two Republican candidates in Alaska, official party nominee Joe Miller and write-in candidate Lisa Murkowski, will win. Incumbent Murkowski lost the GOP primary to the Tea Party-backed Miller and is running as a write-in. If she succeeds, it will be the first time a write-in candidate has won a Senate seat since South Carolina's Strom Thurmond in 1954.
Washington's Senate election may not be resolved for up to a week, Secretary of State spokesman David Ammons said.
As many as 350,000 total ballots may not yet have been counted in King County, chief elections spokeswoman Kim van Ekstrom said early Wednesday. And up to 150,000 ballots may not have been counted outside the county, which includes the city of Seattle, Ammons said.
CNN's Soledad O'Brien, Paul Vercammen, Phil Gast and Mary Snow contributed to this report.