The Nixon administration infamously kept an “Enemies List.” It also infamously subjected individuals and organizations on that list to Internal Revenue Service audits.

Thus, a chilling sense of deja vu accompanied Friday’s news that the IRS, during the 2012 election season, singled out conservative political groups for additional reviews of their tax-exempt status.

There’s no evidence to show that this violation of the public trust rises (or is that sinks?) to the level of the notorious Nixonian example — at this point in time.

But Friday’s apology and brief explanation issued by the IRS should not suffice to make this story go away.

Lois Lerner, who leads the IRS unit that oversees tax-exempt groups, said during a speech in Washington on Friday that the agency flagged groups that included the words “tea party” and “patriot” in their applications for tax-exempt status.

She also said the practice was initiated by low-level IRS workers in Cincinnati and resulted in targeting 75 groups that should not been reviewed.

The IRS released this statement Friday: “Mistakes were made initially, but they were in no way due to any political or partisan rationale. We fixed the situation last year and have made significant progress in moving the centralized cases through our system.”

In this case, though, saying you’re sorry shouldn’t suffice.

Our own Sen. Tim Scott made that correctly clear Friday by saying: “Targeting private citizens on the basis of their political views is completely unacceptable. The White House must not only hold those responsible accountable for their actions, but also assure the American people that these practices are not being employed at other departments and agencies.”

Among the troubling questions that must be answered: Who authorized this practice — and when? Who discovered it — and when? Who ended it — and when?

And how credible is the IRS’ account that low-level workers could trigger such a flagrant perversion of the agency’s proper mission in the first place?

The Associated Press reported Saturday that senior IRS officials learned as early as 2011 that tea party groups were being targeted. The AP cited a draft report from the Treasury Department’s inspector general.

Richard Nixon was rightly forced to resign his presidency over the Watergate scandal. The nation learned of his administration’s appalling use of the IRS as a weapon against political foes during the Watergate hearings.

Subsequent safeguards passed by Congress strengthened safeguards against that abuse of power.

The resumption of that illegal practice, even if only by supposedly low-level workers, demands a thorough investigation.