Sen. Charles E. Schumer (D-N.Y.) has been critical of the proposed reappointment of a Republican Social Security and Medicare trustee. (Yuri Gripas/Reuters)

IN 1983, President Ronald Reagan and House Speaker Thomas P. “Tip” O’Neill (D-Mass.) agreed on a reform package for Social Security. Partisanship is so toxic that it’s hard to imagine today’s leaders agreeing on any issue, let alone reforming entitlements. Quite the contrary: Contemporary politicians are turning an obscure aspect of the 33-year-old Reagan-O’Neill pact into a new bone of partisan contention.

The 1983 deal created “public trustees” for Social Security and Medicare on the theory that the programs’ annual technical documents would gain credibility if reviewed by unpaid outside experts — one from each party — in addition to three Cabinet officers who also had, and still have, that duty. The current public trustees, nominated by President Obama in 2010 and approved by a Senate voice vote, are Robert Reischauer, a Democrat, and Charles Blahous, a Republican. Recently, Mr. Obama reappointed them for new four-year terms, apparently thinking this would be the path of least resistance in the Senate.

He thought wrong. On June 8, all 14 Republicans on the Senate Finance Committee voted to confirm the two men — while all 12 Democrats voted “no.” Democrat Sherrod Brown (Ohio) has said he would raise procedural obstacles to the nominations on the Senate floor.

Democrats claim that the reappointments violated an unwritten “one-term-only” rule for public trustees, or protest that the two nominees have kept their day jobs in which they opine on entitlement programs. But it’s clear their main target is Mr. Blahous, whom they denounced as a Koch Brothers-funded academic who worked on President George W. Bush’s 2005 Social Security “privatization” plan and, they say, has exploited his authority as a public trustee to agitate for cuts in Social Security on various op-ed pages.

In fact, Democrats are campaigning on those talking points in close Senate races, attacking Republican Finance Committee members for their recorded votes in favor of Mr. Blahous.

Mr. Blahous is, indeed, a conservative. He’s skeptical of Social Security and Medicare’s sustainability, as are many other reasonable people across the ideological spectrum — and as the Senate knew when it confirmed him the first time. However, there is no evidence his views have distorted the staff-written trust fund reports, which were also approved by Mr. Reischauer and three Obama Cabinet secretaries. What’s more, Mr. Blahous has told senators that a plan such as Mr. Bush’s is no longer relevant, due to Social Security’s deteriorating cash flow.

As for the “no-second-term” assertion, maybe a fresh pair of eyes should squint at the books. Of all causes Democrats might go to the barricades over, though, that’s a pretty arcane one. Mr. Obama, who is owed senatorial deference on these appointments as on others, didn’t seem to think it was that big a deal.

No doubt the GOP poisoned the atmosphere with its obstruction of Merrick Garland, Mr. Obama’s pick to replace Antonin Scalia on the Supreme Court, and other appointees. But this time, strictly speaking, the Republicans are cooperating with the White House.

The ultimate victim of this petty politicization will not be Mr. Blahous or, as collateral damage, Mr. Reischauer, but the perceived nonpartisanship and objectivity of key government reports — that is, the very values Senate Democrats claim to be upholding.