Republican Mel Martinez (search), a Cuban emigre who left President Bush's Cabinet to run for the Senate, narrowly defeated Democrat Betty Castor (search) to complete a GOP sweep in Senate races across the South.

Martinez will become the nation's first Cuban-American senator.

The former housing secretary held a lead of 79,067 votes out of more than 7.1 million counted in the race to replace retiring Democratic Sen. Bob Graham (search). As many as 250,000 ballots had yet to be counted, but Castor said she didn't think she could gain enough votes.

"This is as close as it gets, in my humble estimation," Castor told reporters in Tampa. "It's not completely over but realistically, truthfully, it would be very difficult to make up the difference."

Martinez had declared victory several hours earlier.

"This is not a night for lawyers. I won. It's over," Martinez said at an Orlando hotel.

Martinez's victory means the Republicans will hold at least 54 seats in the Senate — the result of an Election Day rout that also saw them pick up Democrat-held seats in North Carolina, South Carolina, Louisiana and Georgia.

Martinez campaigned with President Bush several times over the final weeks of the campaign while Castor, a former Florida education commissioner and University of South Florida president, appeared with Democratic John Kerry and running mate John Edwards.

The race was marked by a nasty back-and-forth on Castor's handling of former USF professor Sami Al-Arian (search), who has been accused of funding a Palestinian terrorist group.