The former Massachusetts governor inched up to 572 delegates on Monday -- exactly half the 1,144 needed
-- after the Tennessee Republican Party finalized delegate totals from its March 6 primary. Results in several congressional districts were too close to call on election night, leaving three delegates unallocated.
Romney got all three delegates. He also picked up an endorsement from a New Hampshire delegate who had been awarded to former Utah Gov. Jon Huntsman. Huntsman dropped out of the race in January and endorsed Romney.
Texas Rep. Ron Paul, meanwhile, won a Minnesota delegate over the weekend that had been allocated to former Pennsylvania Sen. Rick Santorum. Santorum won two delegates and Paul won one at Minnesota's 7th Congressional District convention.
Santorum had been projected to win all three delegates, based on the results of local caucuses in February.
Romney and Santorum have been sparring over the delegate count for weeks. Romney's campaign says there is no way for Santorum to reach the number of delegates needed to clinch the nomination, portraying the race as all but over. Santorum's campaign says Romney's numbers are inflated, raising the prospect of a contested convention in August.
According to the Associated Press tally, Romney has more than twice as many delegates as Santorum. Santorum has 272 delegates, followed by former House Speaker Newt Gingrich with 135 and Texas Rep. Ron Paul with 51.
Romney has won 54 percent of the primary and caucus delegates so far, putting him on pace to clinch the nomination in June. Romney could substantially add to his lead Tuesday, when 95 delegates will be at stake in three primaries, in Wisconsin, Maryland and the District of Columbia.
Tuesday's contests mark the midway point in the race for delegates.
A total of 2,286 delegates are slated to attend the party's national convention in Tampa, Fla.
-- 2,169 will be selected through primaries, caucuses and state conventions, while 117 are members of the Republican National Committee, free to support any candidate they choose.
Santorum, who has won 27 percent of the primary and caucus delegates so far, would need 74 percent of the remaining delegates to clinch the nomination before the national convention. Gingrich would need 86 percent and Paul would have to win nearly all of them, which won't happen because most states award delegates proportionally.