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Do progressives have the electoral juice to nudge Massachusetts Democrats further to the left? That is the overarching question posed by the September 4 primary.

Considered as a group, local Democrats are not as far to the left as, say, their compatriots in California. Political viziers consider overwhelmingly Democratic Massachusetts a reliably blue state. And so, it is. Note: the huge independent vote – larger than either of the two traditional parties – leans left.

Still, in 1980 and 1984, voters by narrow margins cast their ballots for Ronald Reagan. That, of course, was then and this is now. But if you look at how the votes tallied in those presidential years, while urban areas voted Democratic, the suburbs rallied for Reagan.

Ever since Michael Dukakis’s election as governor in 1975, the Democrats’ hegemony has rested on a fusion of urban and suburban voters. And while cities by and large have remained bastions of old-style liberalism infused with contemporary progressive sentiment, many suburbs have become more cautious, centrist, and in some cases conservative.

In practical terms, what’s the effect?

A look at the composition of the Massachusetts House of Representatives yields a hint. Of the 160 members, 117 — or 73 percent — are Democrats. Of those 117, at the start of the recently concluded two-year session 54 — or 46 percent — were members of the Progressive Caucus.

This means the center holds slightly better cards than the left. But when you add the handful of House Republicans, and factor in the long term-trend that in 75 percent of the past 32 years the Bay State has chosen a Republican governor (and may well again), you’re left with an image not of Bolsheviks hammering the anvil of class struggle, but rather a bourgeois majority willing to embrace well-targeted social justice initiatives such as a $15-an-hour minimum wage.

This is, admittedly, a view from 30,000 feet. Closer to the ground, conflicts blur and emotions run high. It would be unfair to say that Trump Derangement Syndrome has Massachusetts’ Democrats in a disorienting thrall. But the presidency of Donald Trump has inflamed intra-party tensions over already fundamentally fractious issues concerning immigration, migrants, and refugees.

Six years ago, John Farrell, a former Boston Globe Washington correspondent and biographer of Tip O’Neill and Richard Nixon, wrote in the National Journal about the deep divide that wounds American politics. Farrell concluded that the intellectual divisions run almost as deep as they did in the run up to the Civil War. Since Farrell, a healthy body of thought has emerged to further document the depth and breadth of polarization. And whatever your view of President Trump, he is an unmistakable manifestation of the shrinking center.

Scaling a sweeping political trend to fit the provincial realities of statewide Massachusetts politics is tricky business. Still, it is useful to keep national realities in mind as you try to make sense of the primaries under way.

Polarization is a local, as well as a national, fact of life.

Here are snapshots of four races — one for the U.S. House of Representatives, and three for seats in the Massachusetts House — that illustrate some of the divides among local Democrats.

Rep. Michael Capuano vs. Boston City Councilor Ayanna Pressley

The most dramatic of these is nine-year Boston City Council veteran Ayanna Pressley’s challenge to former Somerville mayor and 20-year congressional incumbent Michael Capuano.

This is a race with multiple subtexts: It’s generational. Pressley is 44, Capuano 68. Gender is in play.

And, race is a factor. The 7th congressional district is the state’s only majority-minority district, snaking from Everett, through Somerville, Cambridge, Roxbury, Mattapan, Milton, and Randolph. Pressley is African-American, Capuano Italian-American.

Ideology, however, is not a major issue. Capuano and Pressley are card carrying social democrats. The differences are in nuance. Pressley, for example, says that under no circumstances would she vote to approve a single penny for Trump’s proposed border wall. Capuano, on the other hand, would entertain such a vote, but only if it could be leveraged to materially benefit current migrants, such as the so-called dreamers. This sort of sliver of a difference could be interpreted as idealism versus pragmatism.

This is what the Pressley-Capuano election is about. “Style,’ according to Alfred North Whitehead, “is the ultimate morality of the mind.” Pressley is an evangelical politician, the possessor of what Lyndon Johnson, a president who employed a wealth of technique, would have called a “preacher-teacher” style. Capuano is a classic Roosevelt-, Truman-, LBJ-, JFK-blue collar, lunch-bucket, bottom-line Democrat. He’s the legislative equivalent of the late Boston Mayor Tom Menino’s “urban mechanic.”

The 7th district is the Massachusetts primary with national significance.

A Capuano victory will be interpreted as Democratic voters having confidence in an official who had to swim upstream against a Republican majority during most of the Obama presidency and who would be able to magnify his accomplishments if the Democrats reclaim a majority the House.

A Pressley win would have a much simpler message: It’s time for a change.

Whoever emerges victorious, expect plenty of comparisons with New York’s Alexandria Ocasio-Cortez’s June upset over Joe Crowley, the House Democratic Caucus Chair. Crowley was widely seen as successor to House Democratic Leader Nancy Pelosi.

As electrifying as the Ocasio-Cortez win was for progressives, she hasn’t been able to sport coattails. Candidates she has stumped for haven’t racked up wins.

A Pressley win might not be as flashy. It will not appear to materialize out of nowhere. But it would be more significant. The 28-year-old undoubtedly charismatic and unabashedly Democratic Socialist Ocasio-Cortez benefitted from a mainstream incumbent who was sufficiently arrogant to remain complacent until it was too late. Capuano never made that mistake.

The Massachusetts State House Races

Of perhaps more granular significance as far as the grass roots of Democratic politics are concerned are the progressive challenges to incumbent state representatives Jeffrey Sanchez, Byron Rushing, and Liz Malia.

Whatever you may think of the pluses or minuses of identity politics, even two years ago it would have been unimaginable for progressives to recruit candidates with the exclusive purpose of defeating a Latino progressive, an African-American progressive, and a lesbian progressive.

But that was before Republican Charlie Baker became governor. It irks many progressive leaders that House Speaker Robert DeLeo has a more intimate working relationship with Baker than he had with his fellow Democrat, Governor Deval Patrick.

Patrick, like his friend, former President Barack Obama, was a master of retail politics. But as with Obama, Patrick seemed temperamentally incapable of cultivating the legislative touch with the same sense of discipline and dispatch.

The seeming lack of comity between Patrick and DeLeo may have been a progressive annoyance. But for some, the entente between DeLeo and Baker is an intolerable outrage.

Primary day is payback.

Paradoxically, the progressive challenges to Sanchez, Rushing, and Malia mimic the tactics used by national Republicans to keep the GOP in line. But as Jerry Seinfeld said in another context, “Not that there is anything wrong with that.”

While the object of these challenges is victory, the headache and inconvenience to the incumbents remain an object lesson in and of themselves.

DeLeo may be electorally untouchable, but some of those around him are not.

Sanchez appears to have been the most vigorously targeted. His opponent, Nika Elugardo, described herself to the Boston Globe as a member of the “super left.” In some districts that would be the kiss of death, but not in the 15th Suffolk which includes Mission Hill, Jamaica Plain, Roslindale, and part of Brookline.

As in the Capuano and Pressley contest, to outsiders the ideological differences are more of degree than kind. But the real sticking point is DeLeo, who in the larger political market place is a centrist liberal.

In the 11th Suffolk District, Malia’s two opponents, Charles Clemons Muhammad and Ture R. Turnbull, don’t seem to have achieved the same degree of traction that Rushing’s opponent has.

Win or lose the 9th Suffolk District, Jon Santiago, a Fulbright Scholar and Yale Medical School graduate has made a strong impression that rests more on his own promise than on Rushing’s relationship with DeLeo.