JOE BIDEN won Massachusetts — by a lot, more even than Hillary Clinton did in 2016, more even than Barack Obama in 2012 or 2008. You have to go back to 1996 to find a Democrat who won Massachusetts by as much as Joe Biden did this year. 

Biden won Massachusetts on his way to winning the presidency with 306 electoral votes and 52 percent of the popular vote. His lead is nearly 7 million raw votes and over 4 percentage points and growing. 

It’s important to state these facts at the outset because, according to a new poll by the MassINC Polling Group, 15 percent of Massachusetts residents think that Donald Trump, not Joe Biden, won the presidential election concluded almost exactly a month ago. A quarter of Massachusetts residents are not confident that the election was conducted in a free and fair manner. 

To repeat: even in deep blue Massachusetts, where twice as many voters voted for Joe Biden as Donald Trump, 1 out of every 4 residents thinks the election was not free and fair. 

As one might expect, there’s a pretty stark divide by presidential vote on these questions. Fully 99 percent of Biden voters think Joe Biden won the presidential election. (It’s hard to get 99 percent of people to agree on the weather in Massachusetts.) Meanwhile, 55 percent of Trump voters think he won, despite all evidence, empirical and judicial, to the contrary. Another 14 percent of Trump voters are on the fence. Only 31 percent are willing to admit reality.

Fully 97 percent of Biden voters are sure that the election was free and fair. Meanwhile, 73 percent of Trump voters disagree. Two-thirds (64 percent) of self-identified Republicans think the same — nearly identical to the 63 percent of Republicans nationally, according to the latest Morning Consult polling. Republican comprise only 14 percent of all residents in Massachusetts, but that small minority is in lock step with the national party on this particular issue.

It’s possible that these Republicans (and Biden voters as well) may be engaging in what’s known as expressive responding: essentially, answering more as a cheerleader for their side than based on their own considered opinion. So maybe most Republicans don’t really believe Joe Biden lost and Donald Trump won, but so long as Trump is insisting otherwise, they feel obliged to tow the party line.

This reflexive, almost tribal, partisanship is a challenge for pollsters, who after all can only report what respondents are telling them. But perhaps it’s better if it’s a problem for polls than for pols. Pollsters can figure out clever ways to get around partisan facades. But how do you govern when a fact as basic as who won the election for the highest office in the land is rejected by a quarter of voters, even in one of the union’s most democratic, wealthiest, and most educated states?