Former Republican Cabinet member Mel Martinez has become the first Cuban-American to enter the US Senate.
Martinez supported President Bush on the Florida campaign trail
Mr Martinez, who came to the US from Cuba aged 15, beat rival Betty Castor to the seat of retiring Democrat Bob Graham in Florida in a close-run vote.
Ms Castor, a former Florida education commissioner, conceded after initially contesting Mr Martinez' one-point lead.
Florida State Governor Jeb Bush, brother of the US President, welcomed the win for Mr Martinez.
The 58-year-old former housing secretary won 49% of the vote to 48% held by Ms Castor.
She told reporters in Tampa on Wednesday: "This is as close as it gets in my humble estimation."
Mr Martinez, who came to the US as part of a church programme to help children leave communist Cuba, had declared victory several hours before she conceded.
Speaking at an Orlando hotel, he said it was "not a night for lawyers", Associated Press reported.
The race to replace Senator Bob Graham was marked by bitter personal attacks on issues including Iraq, war, terrorism and taxes.
Mr Martinez, who left George W Bush's cabinet to run for the Senate, campaigned several times with the president in Florida in the final weeks of the campaign.
Ms Castor, 63, appeared in turn with the Democratic presidential challenger John Kerry and his running mate John Edwards.