Instead, most voters, declaring their independence, have registered as "unenrolled."

But for the vast majority of communities, and for the state as a whole, Democrats do not account for the largest share of the electorate.

Massachusetts is widely known as a blue state that traditionally sides with Democratic political candidates.

Unenrolled voters make up the largest share of the electorate in 332, or about 95 percent, of the state's 351 cities and towns.

In the other 19 communities — including Boston, Springfield, Cambridge, Somerville, Brookline, Fall River, New Bedford, and Amherst — registered Democrats are the biggest group.

There is no municipality in the state where Republicans are the largest group.


Statewide, 54 percent of the nearly 4.4 million registered voters have placed themselves in the unenrolled category; 35 percent are Democrats; 11 percent are Republicans; and the rest, less than 1 percent, are registered either with the Green-Rainbow or United Independent parties.

Unenrolled voters eclipsed Democrats as the dominant group among registered voters in Massachusetts back in 1990 and have increased their lead steadily since.

The trend is also reflected nationwide.

Experts have said that allegiances to the two major political parties have weakened over the years as many voters have been turned off by either party for various reasons — because, for example, they disliked a particular candidate, were disappointed by a scandal, or just tired of increasing partisanship.

"There's been some dissatisfaction at times with the Democratic party and at other times with the Republican party," said Paul Watanabe, political science professor at the University of Massachusetts Boston. "Some people see parties as the establishment and turn away [or] see the candidates as Tweedledee and Tweedledum."

"Generally speaking, after people move from a party status to unenrolled, they stay unenrolled," he added. "So the effect has been cumulative."


In the same way that, decades ago, new voters tended to, at least initially, register with the political parties their parents belonged to, "unenrolled also gets passed on to children," Watanabe said.

There can also be a social advantage to being unenrolled.

"People who are not political activists, which is a big swath of people, they just don't want to talk about which party they belong to," said UMass Amherst political science professor Ray La Raja. "Especially today when politics can be so nasty, being unenrolled is a way of downplaying the kind of talk that might rile social relationships; it's a way of avoiding those types of conversations about politics that can be uncomfortable."

Yet another factor driving people to choose unenrolled when they register to vote in Massachusetts is the state's open primary system, which allows unenrolled voters to vote in any party's primary, rather than just their own.

"To have maximum political flexibility and maximum impact, unenrolled might be the best status," said Watanabe. "If you're locked into one party or the other, you can only get the ballot for that party."

Still, many people who are unenrolled tend to vote consistently with one of the two major parties.

"As the parties get more extreme, people who are kind of in the middle don't feel comfortable saying they belong to either party, but they still tend to vote with the same party. Research shows that doesn't really change," said La Raja.

Experts said the divisiveness of the ongoing election cycle is likely to further fuel the trend.


La Raja said he expects that, particularly at the national level, the Republican party may lose a higher share of its registered voters.

"The party's in trouble — there's no doubt about it," he said.

Matt Rocheleau can be reached at matthew.rocheleau@globe.com. Follow him on Twitter @mrochele