Updated: 11/03/10 9:53 a.m.

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CHICAGO (CBS) – Republican Mark Kirk has defeated Democrat Alexi Giannoulias in the U.S. Senate race.

Kirk was out Wednesday morning thanking voters for sending him to the U.S. Senate and says he wants to get right to work.

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A smiling Kirk greeted Metra commuters at the Ogilvie Transportation Center in downtown Chicago, and many people stopped to congratulate him. Kirk had TV camera crews in tow – as well as Republican Robert Dold, who won election to the congressional seat Kirk is vacating.

Kirk told reporters he hopes to be sworn in as soon as possible. In addition to a full term in the Senate, voters picked Kirk to complete the term for the seat once held by President Barack Obama and now held by Roland Burris.

Kirk promised to work with Obama and says he’ll push to reduce government spending.

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Kirk’s capture of the Senate seat once held by the president, deals an embarrassing blow to Democrats.

Kirk defeated Giannoulias in one of the nation’s ugliest and most closely watched Senate races.

At midnight Wednesday, Mark Kirk addressed the crowd at Westin Chicago North Shore hotel in Wheeling after accepting victory.

“We are 800 miles from any ocean but a tsunami just hit the heartland,” said Kirk. “My name is Mark Kirk and I’m going to replace Roland Burris in the United States Senate. So how about it, Illinois?”

In his speech, Kirk discussed what this victory will mean for the state of Illinois.

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“Tonight, the people of Illinois have spoken. And your vote was heard around the world,” said Kirk. “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, a vote to support the troops, a vote to defend our allies. And in the tradition of this Congressional district, a vote for thoughtful, independent leadership.”

Kirk also discussed the significance of the Senate seat win.

“We saw dark days surrounding this Senate seat. Blagojevich tried to sell it. Democrats blocked a special election to fill it. Washington partisans threw the kitchen sink at us to hold it. But tonight, the sun sets on a one-party corrupt state,” said Kirk. “And this Senate seat was just returned to its rightful owners: the people of Illinois!”

At around 11:30 p.m., Giannoulias conceded to Kirk, speaking to the crowd at his headquarters at the Fairmont Hotel, thanking them for their support and congratulating his rival.

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“Let me begin by congratulating Congressman Mark Kirk. Let’s have a round of applause for Congressman Mark Kirk,” said Giannoulias. “I just spoke to the Congressman and he made a promise to me that he would never forget who he was fighting for. I think he will make a good senator, I think he will make a strong senator, and he’s going to help a lot of people.”

LISTEN: Alexi Giannoulias Gives Concession Speech

Giannoulias went on to thank Ill. Sen. Dick Durbin for his support during his campaign for U.S. Senate.

“Senator Durbin fought for me. Sen. Durbin went to war for me. He worked very hard, he believed in me,” said Giannoulias.

Giannoulias also thanked his supporters.

“Let me say a special thank you to all of you for believing in me, for believing in this campaign. For never forgetting what this campaign was about: people. About putting people first always.”

CBS 2’s Kristyn Hartman reports that Mark Kirk’s hope to make the move from the House to the U.S. Senate is now a reality.

Things got going at Kirk’s headquarters at the Westin Chicago North Shore hotel in Wheeling around 7 p.m. Tuesday. Kirk kept a low profile, saying he would speak when definitive results come in. But he was vocal earlier Tuesday when he voted.

He had a group of supporters at the Highwood polling place where he stopped to talk about a few things: how the Senate race will be one of the most closely watched in the country, how he expects downstate voting to be heavy and pro-Kirk and how busy he’ll be when elected.

“I hope to be that senator to cast the key votes against a trillion dollar spending bill, to defend your right to a secret ballot in a union election, and most importantly, not to have a value added tax,” said Kirk.

Kirk also said people want to send a message this time around, referencing a rising independent tide.

“I think we need a change. This Congress, the Pelosi-Reed Congress, has not worked on spending restraint at all,” said Kirk. “And I think that’s one of the messages we’re gonna take tonight, is that there’s a rising number of Democrats and independents who are also worried that we’re spending too much.”

So what does taking over this Senate seat mean to Republicans?

“I think it’s an interesting anecdote that it was President Obama’s seat. But a U.S. Senate seat is a U.S. Senate seat, regardless of who was occupying it before,” said Ill. Sen. Christine Radogno. “It’s a very important seat to have, so I think that the voters are looking carefully at the individual candidates.”

But DuPage County State’s Attorney Joe Birkett says this is not a referendum on the Republican Party.

“Let’s not lose sight of this,” said Birkett. “Illinois is still a blue state. These Republicans who are elected have to work very hard to earn the trust. And they will. Mark Kirk will and so will Brady.”

Earlier, CBS 2’s Jim Williams reported that people at the Giannoulias headquarters at the Fairmont Hotel were preparing for a long night in this very tight race. Giannoulias needed a significant turnout in the city and Cook County suburbs if he is going to win.

And that’s what Giannoulias predicted as he voted Tuesday morning in the lobby of his Gold Coast condo complex. He appeared upbeat and said he’s done all he can to be competitive.

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“We’ve worked very hard. I’m excited about where we are,” said Giannoulias. “I think the turnout numbers are gonna be strong. It’s gonna be a great day.”

Ill. Sen. Dick Durbin said Tuesday night he believes the Democratic ‘get out the vote’ effort is really going to pay off.

“We had 5,500 people on the streets today knocking on doors; 500 were paid, 5,000 were volunteers,” said Durbin. “We also had 1,500 on phones today. This was a systematic effort. Inspired by the president’s visit, we were determined to get the vote out. I hope that the results show it.”

Durbin says President Obama’s Chicago visit was key to voter turnout.

“Early returns show we have a 70 percent increase in African-American votes in the Chicagoland area over the last off-year election. I think the president’s visit made a big difference,” said Durbin.

Although the race appears final Tuesday night after all the precincts report ballot results, there are still 20,000 to 30,000 absentee ballots in the mail that have to be counted. Ballots postmarked by Nov. 1 are still valid, so the final vote will not be tallied for up to two weeks.

Giannoulias-Kirk Background

Both Alexi Giannoulias and Mark Kirk have weathered their fair share of controversy since winning nomination in February.

It’s been a vicious fight between the two: one is accused of giving loans to mobsters; the other is accused of lying about his military record.

Giannoulias was taken to task over his family’s Broadway Bank, which failed in April. The bank was also the subject of revelations that it loaned $20 million to two convicted felons.

Kirk attacked the management of Giannoulias’ family bank in an October debate.

“He made a number of mistakes, betting his bank’s future on the risky real estate loans, brokered hot money deposits, and loans to well-known convicted felons and mobsters,” said Kirk.

Giannoulias responded: “I am very proud of the community bank that my father started 30 years ago. And let’s be clear, no one has ever suggested the bank has ever done anything illegal, illicit or improper – never.”

Giannoulias would not explain just what he and other bank executives knew about the men’s criminal history before deciding to approve the loans.

Giannoulias read a list of criminals who have donated money to Kirk’s campaign over the years. “If we want to play these guilt by association attacks, let’s do it,” he said.

Kirk responded that he had returned the donations from the people Giannoulias listed.

“When you run big campaigns, you will accept money from a lot of people but then when you hear about criminal problems, you will refund it,” Kirk said. “What I didn’t do, is I didn’t loan money to (convicted political fundraiser and Rod Blagojevich confidant) Tony Rezko.”

Replied Giannoulias: “He hasn’t returned all these contributions. That’s for him to defend. But this goes to the bigger picture of what’s wrong with politics. We don’t talk about issues, we don’t talk about putting people back to work.”

Meanwhile, Kirk has taken heat after he admitted to misstatements about his military record, including claiming to win a “Navy Officer of the Year” award that was actually won by his entire unit.

Giannoulias went after Kirk for misstating his military record in an October debate.

“The question, congressman, is why with this record, would you not tell the truth? Why would you make all this stuff up? Congressman, it’s a simple question. Were you shot at or not?” asked Giannoulias.

Kirk responded: “The ultimate irony that a man who spends most of his campaign for the Senate criticizing my military record, and yet he never served a day in uniform in his life.”

Kirk has apologized for the false statements, saying he had been careless.

Pressed on his strong support for the invasion of Iraq, Kirk claimed the Bush administration had lied to him about evidence that Iraqi leader Saddam Hussein had weapons of mass destruction. The five-term congressman said a Central Intelligence Agency official “absolutely” lied.

When asked about his past claim that he knew with “moral certitude” that Hussein has weapons of mass destruction, Kirk said he based that on a briefing in the White House situation room. Kirk said he was shown various pieces of evidence, such as tubes that supposedly could only be used to refine uranium, and was told they proved the existence of the weapons.

Kirk would not provide details or explain why this seems to contradict a past explanation of the “moral certitude” comment. Previously, he had said he made that statement because Iraqi documents did not account for all of Saddam’s old chemical weapons.

Kirk accused Giannoulias of encouraging class warfare by not supporting an extension of tax cuts for the wealthy. Giannoulias rejected that, saying he opposes the tax cuts because they would add to a huge deficit that ballooned when Kirk and other Republicans controlled Washington.

Giannoulias said Kirk has voted against legislation to make college more affordable, to help women get equal pay for equal work, to crack down on runaway corporate salaries.

“He has an indefensible record in Congress,” Giannoulias said.

Kirk responded that Giannoulias has practically no record.

He noted the 34-year-old’s position as treasurer is his first government job. He also said Giannoulias hasn’t done that job well, noting part of the Bright Start college savings program lost about $150 million on Giannoulias’ watch.

During a discussion of the federal Troubled Asset Relief Program, Giannoulias said he would have pushed for changes in the bailout legislation if he had been in Congress at the time. Kirk said he was trying to have it both ways.

“This is the sort of immaturity of my opponent,” Kirk said. “In the end, a member of Congress is presented with a yes-or-no vote on an always-imperfect package. … In the end, you have to cast a tough vote.”

Giannoulias responded, “If Congressman Kirk is accusing me of flip-flopping, that would be the most remarkable irony in the history of Illinois politics.”

Kirk and Giannoulias plan to meet for a beer Wednesday afternoon at the Billy Goat Tavern, 430 N. Michigan Ave. Kirk says the first round is on him.

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CBS 2’s Jim Williams, Kristyn Hartman, Web Producer Yasmin Tara Rammohan, and the Associated Press contributed to this report.