Conservative Republicans in Washington are demanding a “cleansing” of the FBI, which they are styling as the secret police of the deep state, out to subvert democracy.

Meanwhile, liberal Democrats are talking about the agency that once spied on Martin Luther King and John Lennon as if it were the last defender of civil liberties – a complete turnaround from 2016, when the Democrats were the ones charging that the bureau had interfered politically and cost them the election.

The role reversal is due to Special Counsel Robert Mueller’s investigation into issues surrounding Russian meddling with the 2016 election and possible collusion with Donald Trump’s presidential campaign. Seven months into the probe, it’s clear that this is not ending with a quick exoneration.

The president and his supporters in Congress are bent on discrediting Mueller and the investigation, and they are doing so by tearing down the FBI, which Mueller used to head. His investigators are FBI veterans, including some who have donated to Democratic candidates, and one former member of the team sent snarky text messages that referred to candidate Trump in unflattering terms.

If so, he can join a not-very-exclusive club: Energy Secretary Rick Perry once called Trump “a cancer on conservatism.” Secretary of State Rex Tillerson referred to the nation’s chief executive as “a moron.” Sen. Marco Rubio compared Trump to “a third world strongman,” and Sen. Lindsay Graham called him a “jackass.” All those Republicans are still employed.

The test of any investigation is its product, and we have seen too little of that to draw any conclusions. Almost everyone who works for the federal government is a Democrat or a Republican, but that doesn’t mean that they can’t do their jobs without bias. When it comes to police work, the question isn’t whether cops are biased against crooks, but whether investigators acting under constitutional limits uncover evidence of crimes that can be prosecuted. Judges will decide if the evidence is admissible and jurors will decide if the case has been proved beyond a reasonable doubt.

Until then, everyone else is just speculating about what might happen.

All that we know now about the Mueller investigation, beside the fact that it doesn’t leak information, is that Trump’s former campaign chairman has been indicted on charges of money laundering and other felonies and that two other people, including former National Security Adviser Michael Flynn, have pleaded guilty to lying to investigators about Russian contacts with the Trump team and are now cooperating with prosecutors.

And it may go no further than that. It would be short-sighted for Republicans to erode public trust in the FBI and the criminal justice system just to save the Trump administration from further embarrassment. It would also be a mistake for Democrats to stop asking questions about interference by law enforcement in politics just because they happen to like where this investigation seems to be headed.

If nothing else, the last year should have shown all Americans how quickly the political winds can change, and how important it is to have strong, independent institutions that can check and balance each other’s power. That’s something everyone should be able to value, no matter where they stand on the partisan divide.