A record number of Massachusetts voters could cast ballots in Tuesday's presidential primaries, although most of those eligible to vote are not expected to do so, according to the state's top elections officer.

Interest in the Republican contest, which features multiple candidates, could drive overall turnout north of 42 percent, Secretary of State William Galvin said during a briefing Monday.

Galvin, comparing the 2016 presidential contest to the last open contest for the White House in 2008, said that based on key indicators he believes turnout on Tuesday, when Massachusetts joins multiple other states in voting, will "hopefully meet and perhaps exceed" the 1.8 million votes cast eight years ago.

"My opinion at this point is that we're going to have a very good turnout tomorrow," Galvin said, indicating that he believes 2008 set a record in the Bay State for primary voting. Galvin does not think votes cast will reach the 2 million mark.

The Brighton Democrat said he bases some of his high hopes for turnout on the fact that an historically high number of absentee ballots - 83,000 - have already been cast and the GOP race where businessman Donald Trump's rise to the top of the polls in Massachusetts and nationally has generated an extreme level of interest.

While 501,000 people cast votes in the 2008 Republican primary between rivals Mitt Romney and John McCain, Galvin said he thinks as many as 700,000 GOP ballots could be pulled on Tuesday.

"I think it's obvious to everybody that the nature and tenor of the Republican presidential contest, both here in Massachusetts and throughout the country, is very different than almost any Republican event that we've seen in recent times," Galvin said during a pre-election briefing with the media. "You might say that the Romney-McCain fight was kind of a tennis match. This is kind of world wrestling."

Since Jan. 1, Galvin said, almost 20,000 Democrats have unenrolled from the party with the majority - 16,347 - moving to unenrolled status, while 3,455 former Democrats enrolled as Republicans Conversely, 5,911 Republicans unenrolled to become independent voters.

Independent voters can choose to vote in either primary, but Galvin sees the trends as favoring a high turnout in the Republican contest.

On the Democratic side, Galvin said that both former Secretary of State Hillary Clinton and Vermont Sen. Bernie Sanders have run aggressive campaigns in Massachusetts, making visits and investing in advertising and ground operations. However, he said he's not sure the enthusiasm in that contest can rival the 2008 race between Clinton and then-Sen. Barack Obama when 1.2 million voters pulled Democratic ballots.

Absentee balloting, barring special circumstances, ends at noon on Monday. As of Monday morning, Galvin said 83,000 people had voted absentee, including 25,000 Republican ballots.

Clinton and Sanders were both in Massachusetts on Monday trying to rally their bases ahead of Super Tuesday. Clinton campaigned in Springfield and had an event planned at the Old South Meeting House in Boston in the afternoon, while Sanders planned a rally in the evening at Milton High School. Former President Bill Clinton also plans to headline a late-night rally for his wife in Worcester.

On the Republican side, Ohio Gov. John Kasich, who has been running in third in Massachusetts in some polls, planned a late afternoon rally in Plymouth.

The latest Suffolk University poll conducted between Feb. 25 through Feb. 27 showed Clinton leading Sanders by eight points with 50 percent support to Sanders's 42 percent. Clinton held a sizeable lead with 57 percent of registered Democrats, but trailed among the state's largest voting bloc - independents - 54 percent to 37 percent.

Massachusetts counts 4.27 million registered voters, including those considered "inactive" but who are still eligible to vote on Tuesday. Of those, 2.28 million are not enrolled in either party, while only about 468,000 are registered Republican voters.

Trump led the Republican field in the latest Suffolk poll released over the weekend with 43 percent to Florida Sen. Marco Rubio's 20 percent. Kasich, despite the highest favorability rating of anyone in the GOP field among likely Massachusetts GOP primary voters, polled in third in the state with 17 percent followed by Texas Sen. Ted Cruz at 9 percent and retired neurosurgeon Ben Carson at 4 percent.