WASHINGTON -- How do you write a platform for a party whose candidate's positions span the unfortunate gamut from nonexistent to offensive to flatly at odds with those of the party?

Such is the thankless task consigned this year to Sen. John Barrasso. The Wyoming Republican is a Yale-trained orthopedist with a voracious appetite for history (he's currently immersed in a Ulysses S. Grant biography) and a political junkie's love of game and country (Barrasso hasn't missed an inauguration since his father, a Pennsylvania cement finisher, took him to John F. Kennedy's).

Barrasso exhibits a wonk's inclination for policy specifics (he just hosted surgeon and writer Atul Gawande to speak to fellow senators on health care) that puts him more in the "sweat the details" spirit of Hillary Clinton than the details-shmetails approach of Donald Trump.

Barrasso is, in short, the anti-Trump. Not in the sense of being opposed to the nominee -- he isn't, although, like most of his GOP Senate colleagues, he scarcely exudes enthusiasm for Trump.

But where Trump has dispensed campaign cash to both parties, veers from stance to stance, and displays a hummingbird's attention to specifics, Barrasso is resolutely conservative and serious about the enterprise.

And in a conversation with The Washington Post editorial board the other day, Barrasso presented the platform-writing exercise -- it will take place in Cleveland the week before next month's convention -- as a mechanism both for defining a party reeling from the Trump phenomenon and for educating its nominee.

So, I asked, does the platform matter in the age of Trump?

"It does to me. It does to the party," he replied. "It really is who we are, what we believe in, what our values are. That's why I think it matters now more than ever."

Specifically, Barrasso continued, "it matters in terms of being instructive to our nominee for president. I've talked to him and asked him to embrace it and I believe that he will."

How interesting to understand the platform as an instructional document ... for the top of the ticket. One illustration of that needed instruction came as we pressed Barrasso on the question of whether, as he sees it, Trump -- and his calls for a wall on the Mexican border, deporting illegal immigrants, and barring and profiling Muslims -- represents Republican values.

"To me, tone matters," Barrasso said. "I'm from Wyoming. We tend to be respectful, positive, inclusive, and that's what I would like to see in the platform."

Yes, but. When speaking with Republican politicians and elected officials, it is always, yes, but. They talk tone and respect, yet they have to deal with the reality of a nominee of unparalleled vulgarity and offensiveness.

"I have concerns with a number of things our nominee has said," Barrasso allowed. "It's not the way I would say them." On one level, this is an infuriatingly mild rebuke to Trump's provocations.

On another, I confess some sympathy for Barrasso et al. It's easy for folks like me to demand that they renounce Trump. It's much harder when you've got an election coming -- not just for president -- and a party to hold together.

And so, the platform, an exercise that features quadrennial hurdles. On the Republican side, these include language on abortion and gay rights, the latter particularly interesting because this will be the first platform written since the Supreme Court's ruling on same-sex marriage.

But the Trump phenomenon heightens the challenge for the 112 delegates chosen to assemble the document.

First, whether and how to incorporate -- respectfully, no less -- Trump's trademark positions. Will the platform mention the wall? Call for mass deportations? Envision an immigration ban, however temporary?

Second, even assuming those issues can be elided through artful drafting, how to reconcile Trumpian stances -- against free trade, against entitlement reform -- with long-standing, and conflicting, GOP doctrine?

The 2012 platform lauded free trade agreements for having "facilitated the creation of nearly 10 million jobs" and lamented the Obama administration's "deplorable ... slowness" in completing pacts -- including the Trans-Pacific Partnership that Trump now denounces. It emphasized the need to "restructure" entitlements, including raising the Medicare eligibility age. Trump has vowed to "save Social Security and Medicare without cuts."

How to harmonize these positions? The platform, Barrasso said, quoting his Wyoming colleague, Sen. Mike Enzi, an accountant, should be seen as "a sales brochure, not an audit." Even without having to meet generally accepted accounting principles, that is one hard job in this year of Trump.

(c) 2016, Washington Post Writers Group