Robert Mueller is looking for the truth behind an allegation that will dog the presidency of Donald Trump for as long as he holds the office.

Yet the president calls the search an “American disgrace.”

It is no such thing.

The disgrace is being generated from another source. The Oval Office has produced a disgraceful example either of extreme naivete or willful ignorance or — in the worst case — of deliberate deception.

I don’t know which it is. The president has signed on to the continuing disparagement of the FBI, the Department of Justice and other intelligence agencies that stand by their combined assertion that the Russian government intervened in our 2016 presidential election.

Trump won’t acknowledge publicly what he must: that the intelligence agencies’ assessment is accurate.

I want to stipulate that I do not know if the Russian interference determined the election outcome. I haven’t seen any evidence that votes were changed or that local local elections officials were compromised. Maybe none exists of actual impact on the outcome.

Whether it did or didn’t, the issue is that the Russians meddled. The operative question is whether the Trump campaign was complicit in that act of aggression against our electoral system.

Mueller was selected to find the truth. Republicans and Democrats sang together in praise of Mueller’s appointment, which came from Deputy Attorney General Rod Rosenstein after AG Jeff Sessions recused himself from anything dealing with the Russia probe.

The disgrace is occurring now as Republicans are seeking to discredit Mueller, whose integrity once was considered impeccable. If the president fires Mueller, or Rosenstein, or both of them, then the disgrace moves into another category altogether.

Then we’re talking about a certifiable constitutional crisis.

Trump’s definition of “disgrace” needs work. It’s not the search that disgraces the nation. It’s the attempt to derail it that gives millions of Americans serious cause for concern.