In a “Scott Brown report” radio ad, the senator declares that in the coming “Taxmageddon” — that is, the year-end expiration of both the Bush income-tax cuts and the Obama payroll-tax cuts — “the hardest hit will be the middle class, with families seeing an average increase in their tax bill of $4,138. Yet, some people are eager to see tax rates rise.” What Brown doesn’t say is that he himself, as a self-described centrist Republican willing to cross the aisle, could do a lot to help the middle class avoid this fate.

President Obama and most Democrats in Congress are willing to extend the Bush tax cuts for everyone earning less than $200,000 a year and families with less than $250,000. Some Democrats are willing to compromise on extending the cuts for all families earning less than $1,000,000. Brown, however, has held out for the conservative litmus-test position of nothing short of extending the Bush tax cuts for all. That’s fair enough, as a policy ideal. But if Brown were to break with the GOP pack and declare his willingness to extend the middle-class tax cuts now, and worry about the others later, it would be a powerful, potentially game-changing gesture — the work of a courageous centrist blazing a path toward the kind of common-sense compromise Brown likes to talk about.

Instead, he’s joining his party leadership in refusing to consider a compromise, lest it sap Congress’ willingness to extend the tax cuts for the rich. It’s this type of brinkmanship — essentially, holding the middle-class portion of the tax cuts hostage in hopes of getting the whole enchilada — that most Massachusetts voters abhor. If Brown wants to show how a centrist Republican from Massachusetts can really make a difference — cutting through the ideological log jams — he should do it now on taxes. It would go a long way toward justifying his reelection.