U.S. Rep. Ed Markey will win Tuesday's special U.S. Senate election in Massachusetts and serve the remainder of fellow Democrat John Kerry's term, CNN projects.

Markey defeated GOP businessman and former Navy SEAL Gabriel Gomez.

The Democrats' majority coalition in the Senate remains 54-46.

Markey will serve Kerry's remaining year-and-a-half term. The seat is up for a full six-year term in 2014.

Kerry stepped down earlier this year to become U.S. secretary of state.

Markey, who has served 20 terms in the U.S. House, was consistently on top of Gomez in public opinion polls, including a 10-point, 52 percent to 42 percent lead in a Suffolk University survey of likely voters released Monday and a 49 percent to 41 percent advantage in a Western New England University poll released Sunday.

The race was marked by its nastiness, with both candidates leveling charges of hyper-partisanship to try and sway voters in the Bay State.

Markey demanded Gomez release more of his income tax returns to shed light on a real estate transaction. Gomez suggested Markey wasn't a valid resident of Massachusetts after three decades in Washington.

Gomez called Markey "pond scum" for airing an ad that pictured him alongside Osama bin Laden. And Markey cast doubt on Gomez's past as a private equity investor since Gomez wouldn't disclose his list of clients.

Republicans had hoped to repeat Scott Brown's surprise victory in the 2010 race to fill the remaining two years of the late Sen. Edward Kennedy's term.

Then-state Sen. Brown defeated Martha Coakley in a come-from-behind victory then but lost his re-election bid last November to Democrat Elizabeth Warren.

No Republican upset this time

While the GOP looked to comparisons to the 2010 special election and Gomez aides predicted a similar shocker, much has changed since Brown's upset victory.

President Barack Obama's health care measure was facing key votes in Congress at the time, and Brown's victory gave Republicans a key 41st seat in the Senate, allowing them to filibuster Democratic initiatives such as Obamacare.

The tea party movement, formed less than a year earlier, was on the rise, and played an important role in support of the charismatic Brown. And many national and state Democrats took the seat for granted as it had been in the party's hands for decades.

While there was still a lot at stake in the election (a GOP upset would have taken a bite out of the Democrats' slim 54-46 majority in the Senate), and while partisanship is still just as bitter in the nation's capital, the climate has changed a bit, and the seat is not considered a crucial vote in any upcoming legislation.

But Democrats weren't taking anything for granted this time around.

"Gabriel Gomez was no Scott Brown and Ed Markey was no Martha Coakley from the 2010 election," said David Paleologos, director of the Suffolk University Political Research Center.

Another difference: While Markey had the advantage Tuesday, three years ago Brown had closed the gap and took a small lead in the final pre-election polls.

"In January of 2010, independents broke to Brown by a 65-30 advantage which propelled him to a 5-point statewide win," said Paleologos, who predicted that Gomez would carry independents but not by enough of a margin to close the gap with Markey.

Less than half of Massachusetts voters said they had a lot of interest in the election, according to the Western New England University Polling Institute. The 42 percent who said they have a lot of interest was lower than the 58 percent who said the same thing in advance of the 2010 gubernatorial election in Massachusetts, and the 82 percent who felt the same way just before last November's presidential election.

Special elections often draw low turnout, and this race did not appear to be an exception. The contest generated little interest with the public even before it was overshadowed by April's Boston Marathon bombings, which killed three people and injured nearly 300.

Election had to compete with sports

Last week, Massachusetts Secretary of State William Galvin said that he was "extremely concerned" about low turnout. According to the secretary of state's office, 13,000 fewer absentee ballots had been requested one week before the June 25 election compared to the 2010 special election. Fifty-four percent of voters cast ballots in that contest, around the same percentage as the 2010 election for governor.

"With many people focused on the (NHL's Boston) Bruins playing in the Stanley Cup final, the (Whitey) Bulger trial, and the end of the school year, the special election has a lot of competition for attention," Galvin told reporters.