Lynda Connell, a 50-year-old registered nurse from Whitman, said she voted for Brown because she believed he was willing to work with Republicans and Democrats.
"He's very bipartisan, and he's voted on the issues, not just by the party," Connell said.
Connell said she voted for Romney for fiscal reasons.
"He's run a major company. I liked him when he was governor. I think he did a good job," she said.
Romney drew high security when he and his wife cast their ballots in suburban Belmont, which they still call home. They later traveled to Ohio and Pennsylvania for last-day campaigning in key swing states before returning to Boston, where supporters had gathered at the city's convention center.
Massachusetts Secretary of State William Galvin said mostly anecdotal reports around the state pointed to a strong turnout, with long lines at some polling places. He said he had received relatively few reports of major voting problems and most had been resolved.
Voters said yes to ballot Question 3, allowing marijuana to be used medically for people with cancer, AIDS, Lou Gehrig's Disease and several other conditions. The law would create nonprofit medical marijuana treatment centers regulated by the state Department of Public Health.
Also approved was Question 1, which requires automakers to share diagnostic and repair information with independent mechanics. The Legislature approved a compromise version of "Right to Repair" in July, but it was too late to remove the question from the ballot.
Voters were also deciding Question 2, which would allow doctors to prescribe life-ending medication at the request of certain terminally ill patients. The results were too close to call early Wednesday.
Besides Tierney, Democratic incumbents carried the day in the state's other House races.
Rep. Edward Markey, the dean of the state's congressional delegation, defeated Republican Tom Tierney in the 5th district; Rep. Niki Tsongas bested Jon Golnick in the 3rd district; freshman Rep. William Keating defeated Christopher Sheldon in the 9th district; Rep. Stephen Lynch won over Republican Joe Selvaggi in the 8th district; and Rep. Michael Capuano won over independent Karla Romero in the 7th District.
Rep. Richard Neal in the 1st District and Rep. James McGovern in the 2nd District were unopposed Tuesday.