With an all-Democratic congressional delegation, an all-Democratic roster of statewide officeholders, and the most lopsidedly Democratic state legislature in America, Massachusetts deserves its reputation as the bluest of blue states. Yet most registered voters in Massachusetts don’t have a “D” after their names. Unenrolled voters – those not affiliated with any political party – have outnumbered Republicans and Democrats for nearly three decades. Of the state’s 4.26 million voters, more than 2.2 million, or 53.1 percent, do not specify a party affiliation.

Judging by results, of course, most of the state’s unenrolled voters lean Democratic, even if they decline to wear the party label. But not all tilt leftward. Some – like me – incline distinctly the other way. And since Massachusetts permits unenrolled voters to participate in either party’s primary, it’s a safe bet that some of those choosing the Democratic nominee for governor in next week’s election will be conservatives or libertarians apt to vote for Republicans in a general election.

Republican-leaning unenrolled voters have a compelling reason to vote in Democratic primaries: In this state, that’s where most of the action is. Now and then, the beleaguered Massachusetts GOP treats itself to a dynamic primary contest, such as the three-way battle last year among US Senate hopefuls Gabriel Gomez, Michael Sullivan, and Dan Winslow. But those are few and far between. In this year’s Republican primary, self-made businessman Mark Fisher is plainly the more stalwart conservative, but he has virtually no chance of beating Charlie Baker to become the party’s nominee for governor.

The Democratic nomination, however, isn’t a foregone conclusion. Attorney General Martha Coakley, Treasurer Steve Grossman, and health-care guru Don Berwick are all running as very liberal Democrats, and I can’t see myself voting for any of them in the general election on Nov. 4. But that’s no reason to sit out the primary election, where my vote is more likely to have an impact. All I have to decide is which of these three lefties to vote for.

Should I vote strategically, backing the Democrat I think has the least chance of winning in November? Should I support the candidate whose abilities and experience seem most suited for executive office? Should I try to figure out which of the three Democrats might at least be open to considering reforms and innovations proposed from the right?

I put the question to Coakley, Grossman, and Berwick last week: “How would you make the case to unenrolled voters who don’t share your overall political ideology, but who plan to take a Democratic primary ballot on Sept. 9, that they should vote for you to be the Democratic nominee for governor?”

Coakley responded with some wholly nonresponsive boilerplate.

“I am running to be governor of the whole Commonwealth,” her statement began. “Regardless of political ideology, I believe we can work together to create an economy on our terms, not Wall Street’s.” She ticked off the predictable catchphrases – “access to early education,” “cutting red tape,” “building our regional economies,” blah blah blah, ending with a nod to “policies that cross political lines and will benefit everyone in Massachusetts.”

Grossman’s reply focused on his career as “a successful business owner and proven jobs creator,” and emphasized reforms he implemented as state treasurer. Among them: “putting the state’s checkbook online and bidding out all major contracts, which resulted in tens of millions of dollars of savings.” As governor, he said, he would try to “make our entire state government faster, more flexible, and more entrepreneurial.”

Berwick described in detail his long private-sector experience in health-care management, and his particular interest in bringing techniques of modern management and quality-control to the medical industry. He made the insightful point that precisely because the “progressive agenda requires trust in government,” it is critical for Democrats not to squander that trust through scandals and fiascos, such as those at the Probation Department and the state’s Health Connector website. And he said his fellow-liberals are too inclined to fear what businesses “will get away with” and not concerned enough about the harm states cause when regulations are too onerous.

As a free-market conservative who favors less government, I wouldn’t want the commonwealth’s leading advocate of socialized medicine to succeed Deval Patrick as governor. Berwick proclaims himself the most left-wing candidate in the Democratic field, and I agree with almost nothing he stands for.

But I’d much rather see Democrats nominate a candidate who isn’t a political insider. And I want voters to have a choice in November that makes the differences between the parties as vivid as possible. Coakley and Grossman are serious candidates, but Berwick strikes me as the more serious Democrat. He won’t get my vote in the general, but the primary is a different story.

(Jeff Jacoby is a columnist for The Boston Globe).