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Barack Obama (search), who shot from obscurity to political stardom with his message of national unity, trounced Republican Alan Keyes (search) at the polls Tuesday to be elected the fifth black U.S. senator in history.

"We can look forward to the future. We can build step-by-step to ensure we arrive at the practical commonsense solutions that all of us hope for," Obama said as he claimed victory Tuesday night.

Obama overwhelmed the conservative commentator and former diplomat Keyes in the nation's first U.S. Senate race between two black major-party candidates.

With 73 percent of precincts reporting, Obama had 73 percent, or 2,515,350 votes, and Keyes had 24 percent, or 844,108 votes, in unofficial returns. Two third-party candidates split the rest of the vote.

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Keyes, in a combative speech Tuesday night that stopped short of conceding the race, vowed to fight the corrupt politicians. He said his supporters provide a foundation for a campaign to clean up Illinois.

"On that rock we shall build a house of integrity for the people of Illinois," Keyes said.

Obama enters the Senate already boasting a national reputation and a list of politicians grateful for his help.

The 43-year-old liberal state senator from Chicago catapulted to political prominence with a stirring keynote address at the Democratic National Convention. The speech made him a draw at political events across the country, able to raise money and attract media attention.

Running against Keyes, who never posed a serious threat, gave Obama the freedom to make the most of his new stardom. He was able to donate campaign money to other candidates instead of spending it on his own race and take time to appear at rallies and fund-raisers across the country.

"He's gonna walk in the door with a lot of friends," said Sen. Dick Durbin, D-Illinois.

But the man Obama replaces, Republican Sen. Peter Fitzgerald, cautioned that Obama's high profile might work against him, especially among those thinking of future presidential campaigns.

"Some of his colleagues in the Senate may see him as competition," Fitzgerald said. "Some people will be grateful and will return the favor, but others ... may be secretly trying to undermine him."

Even before Obama has taken office, nearly half of Illinois voters think he would make a good president, according to exit polling.

Keyes, 54, who twice lost bids for president and for U.S. Senate from his home state of Maryland, moved to Illinois to challenge Obama after the original Republican nominee dropped out.

Keyes pledged to reinvigorate an Illinois Republican Party scarred by corruption scandals. But his strong focus on morality and his penchant for controversy strained relations between the conservatives who drafted him and the moderates who predicted it would be hard for him to win in the Democratic-leaning state.

He often instigated controversy in the campaign. He described Obama as a socialist and compared his position in favor of abortion rights to that of slaveholders.

There were major differences between the candidates on the war in Iraq, taxes and social policy. But Keyes focused on abortion and gay rights and lacked the resources to mount a major attack on Obama, who often dismissed his opponent as out of touch.

"The man is always lecturing. I will not be lectured to," said Chicago voter Charlene Parks-Ward, 57.

In contrast, Obama portrayed himself as someone who can unite people despite racial and political differences.

He offered his own life as an example of what can be achieved by bridging differences. The son of a black man from Kenya and a white woman from Kansas, he was raised in Hawaii and Indonesia, became the first black president of the prestigious Harvard Law Review and ended up teaching constitutional law at the University of Chicago.

Obama is "young, vibrant and presents new hope," said voter Chester Tindall, 53, a Democrat from Chicago.

Obama won the support of nine out of 10 black voters and seven out of 10 white voters, according to voter interviews conducted at the polls Tuesday for The Associated Press by Edison Media Research and Mitofsky International. About 40 percent of Republicans backed Obama, as did 75 percent of independents.

Keyes drew his strongest backing from white Protestant conservatives, according to the poll of 1,392 Illinois voters. Results were subject to sampling error of plus or minus 4 percentage points, higher for subgroups.