Massachusetts politics underwent a minor revolution Tuesday night when Democratic state Treasurer Shannon O'Brien, favored in late polls to win the governorship from the Republicans, was soundly defeated at the ballot boxes by Republican Mitt Romney.

Romney won 51 to 44, with 79 percent of the precincts reporting.

The victory by Romney -- head of the 2002 Salt Lake City Olympics Committee, political prodigy and one of People magazine's 50 Most Beautiful People -- means the GOP can keep the sole Republican statewide seat in a massively Democratic state.

When O'Brien first stepped in, the race turned to an unexpectedly close call, with O'Brien leading in the latest polls even though Romney spent $30 million of his own money compared to $6 million spent by O'Brien.

But, like most New Englanders, Massachusetts voters are concerned about the economic slump. O'Brien's background as treasurer had come back to haunt her because of the state's budget shortfall of about $300 million.

"In the Treasury, she's raised her budget from $5 million to $6 million in her personal staff. She's raised her own salary by 65 percent. That is not the kind of experience we need," Romney said.

O'Brien tried to get a stir out of voters after Romney called her "unbecoming" during their last debate.  Romney was making a reference to O'Brien's characterization of his record. New York Sen. Hillary Clinton accused Romney of gender stereotyping. It's uncertain whether the spat affected voters -- but women broke for O'Brien while men leaned toward Romney.

An O'Brien victory would have made Massachusetts -- home of the Kennedy dynasty -- a one-party state for the first time since the 1990, when Michael Dukakis left the governorship. The state Legislature has a veto-proof Democratic majority, the entire congressional delegation is Democratic and registered Democratic voters outnumber Republicans three to one.

Fox News' Carl Cameron contributed to this report.