Although policy differences between Congressman Michael Capuano and challenger Boston City Councilor Ayanna Pressley may be wafer thin, one has emerged and it may be a reminder that Democratic primary voters want their policy unleavened with legislative realities.

Capuano would vote some funding for Donald Trump’s border wall in exchange for progress on protecting Dreamers and comprehensive immigration reform. Pressley would not under any circumstances vote funds for the border wall. And actually, neither thinks much of the wall. As reported by State House News Service’s Andy Metzger, here is Capuano’s take:

“I got to be honest ... I don’t care about a wall one way or the other, it is a nothing issue to me,” Capuano told business leaders on Tuesday morning. “It’s a stupid idea. It’s a complete and total waste of money, but if he needs this political victory to some extent, I’m not going to give him $25 billion, but I’d give him something to play and say, ‘Oh look my wall,’ as long as he gave us real immigration reform so we don’t have to play this game again.”

Councilor Pressley responded:

“Around many issues, I have been and will continue to be willing to work with many diverse groups,” Pressley said in a statement responding to Capuano’s comments. “When it comes to protecting the most vulnerable among us, however, there can be no mistake: we must ensure that we don’t spend a penny on our president’s delusional border wall, and that at-risk communities in the district and across the country are protected from the bigoted policies coming from the Trump administration.”

We’ve seen this party primary practicality-purity split play out before. Back in 2009 a version of health care moved out of the House to the Senate that included restricting federal funding for abortions. Senate candidate Martha Coakley proclaimed that no way, no how would she vote for health care legislation that included the abortion provision. Her leading opponent for the nomination immediately decried her naiveté for not understanding how the legislative process works.  Sensing political weakness, Coakley doubled down and attacked her adversary for heresy to true Democratic values. Within twenty-four hours the chastened pragmatist relented and stated that he too would vote against the health care bill unless the abortion language was excised.

And that pragmatic politician was, of course, Congressman Michael Capuano.

The wall doesn’t have the bite in a Democratic primary that abortion does. Still, even though Capuano called the wall a “stupid idea,” “complete and total waste of money,” and mocked Trump in the bargain, the purity edge has to go to the uncompromising Pressley.

If the wall does go up, we’ll have to tear it down when America returns to a moderate level of sanity. That will provide jobs for hard hats, including many Mexican and Mexican-American laborers. I propose we issue them red baseball caps with the legend “Tear down this wall” and red, white and blue t-shirts identifying them as the “Reagan Brigade.”