Trust, once broken, is hard to regain.

Certainly that old chestnut applies to the recent revelation that some IRS officials were about as impartial as a political attack ad as they went about their duties.

That the IRS would target conservative groups for especially keen scrutiny when they applied for tax-exempt status is troubling enough.

But the truly frightening aspect of this scandal is that it raises the specter that the agency might have engaged in similar political profiling, only in ways potentially more harmful and punitive to Americans.

It’s entirely conceivable that IRS agents also used political affiliations to decide which individual taxpayers or businesses to audit.

Or, as appears to have been the case with the clandestine profiling of groups seeking tax-exempt status, that the agency relied on such information to decide who wouldn’t receive extra attention from the federal tax-collecting apparatus.

If there is anything positive to be said about the current situation, it’s that the IRS’ transgressions were so blatant that we doubt Congress will cut any corners as it investigates.

We hope not, anyway.

No agency deserves more than the IRS to have its actions subjected to a merciless, but fair, examination.