Colin Graham, a spokesperson for Winslow, dismissed claims that the low turnout would benefit the most conservative candidate.

“We’ve made over 150,000 live—not automated—calls to likely GOP voters,” Graham wrote in an email. “In a low turnout election, that kind of investment is going to pay huge dividends.”

Despite weak performances in public polling, Winslow, who is considered the most liberal of the Republican candidates, has won the endorsements of the Boston Globe, the Boston Herald, and the Springfield Republican, and a recent advertisement from his campaign claims that he has been endorsed by every major paper in Massachusetts.

Graham said that daily internal polling conducted by the Winslow campaign showed the race close between the three Republicans.

“Some days Sullivan is on top, sometimes Winslow,” Graham said of the surveys. “Our tracking shows Gomez having the least amount of identified, confirmed voters.”

Polls open at 7 a.m. Tuesday morning and close at 8 p.m. in the evening. The winner of the Democratic primary will face the winner of the Republican primary in a special election on June 25.

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