Supporters of Democratic Senate candidate Edward J. Markey talk as they await election results at a gathering at Boston Park Plaza Hotel and Towers in Back Bay on Tuesday evening.

BOSTON—As the final voters cast their ballots in the state’s special election Tuesday evening, the two men vying for the Commonwealth’s open Senate seat gathered with supporters at two hotels here to take in returns and, they hoped, to celebrate a victory.

At the Boston Park Plaza Hotel and Towers in Back Bay, supporters of U.S. Rep. Edward J. Markey, the veteran Malden Democrat that analysts expect to win the election, gathered before a massive American flag and a well-stocked bar and buffet. Markey, who has served in Congress for 37 years, has had the support and assistance of influential Democrats from the start, including U.S. Senator Elizabeth Warren, Secretary of State John F. Kerry, President Barack Obama, and a host of other officials. In April, he cruised to victory in the Democratic primary over South Boston Congressman Stephen F. Lynch.

Markey’s opponent, Republican businessman Gabriel E. Gomez, gathered his supporters at the Seaport Boston Hotel. After an easy victory in the Republican primary in April, Gomez, a former Navy SEAL, has struggled to drum up the same swells of support that propelled then-state senator Scott P. Brown to a surprise victory over state Attorney General Martha Coakley in a special Senate election here in 2010.

On Monday, Massachusetts Secretary of State William F. Galvin, the state’s chief election official, predicted a record low turnout of just 1.6 million voters, or about 37 percent of the Massachusetts electorate. Conversely, in the 2010 special Senate election, more than half of the electorate went to the polls, in part representing a surge of independent voters who supported Brown.

—Staff writer Matthew Q. Clarida can be reached at clarida@college.harvard.edu. Follow him on Twitter @MattClarida.