Republicans are really mad at Eric Holder.

You can see it in Darrell Issa’s irate questioning of the Attorney General. Within the span of one minute at a House Oversight hearing, for example, you can hear Issa interrupt, chide and scowl at Holder, at one point scolding him,“You’re not a good witness! A good witness answers the question asked.” (This excerpt even has Issa channeling Al Pacino, as he thunders, “The lady is out of order!”)

It may be understandable that many are angry with Holder, given the serious allegations in the IRS and AP investigations this week.

But the heated exchange with Issa had nothing to do with those issues.

It was from a hearing last year, over a now forgotten dispute about the “Fast and Furious” gunwalking program. (Issa received internal emails from the Justice Department about the program, and then wanted the Justice Department’s internal emails about responding to the original request.) The history is instructive because it is the hidden mantle beneath this week’s dispute. The two men clashed in another dramatic exchange at Wednesdays’ House Judiciary hearing. Last year, Issa was so mad at Holder that he led the House GOP down an unprecedented course.

On June 28, 2012, the House of Representatives voted–for the first time in American history–to hold an Attorney General in criminal contempt. There have been many battles between Congress and the executive branch in our history, but no Congress ever took the extraordinary step of seeking criminal charges against the nation’s chief law enforcement official.

So while it’s popular to say our politics are polarized, and “both parties” are to blame, as a matter of historical fact, this House GOP is set a new precedent for politicizing the oversight process.

How many times can they overplay their hand?

Now, as the Justice Department is under scrutiny for seizing the AP’s phone records and it begins an investigation into the IRS, Republicans have already used up their most significant oversight power against the attorney general–and over a much smaller matter. (What are they going to do, vote for contempt again?)

Since Washington always begins with politics, the first analysis of the Republican predicament–call it Obama Scandal Obsession–is that Issa’s approach could hurt the G.O.P. as a party.

On Wednesday, The National Review warned Republicans that “scandal is not an agenda,” and they should not think scandals will “deliver election victories in 2014.” Charles Krauthammer and Bill O’Reilly have also jumped in, urging Republicans to stop putting Obama-bashing ahead of the facts. (Again, there are no reports that the IRS or AP decisions originated in the White House, so far, these are distinctly Obama-less stories.)

Yet beyond any self-inflicted damage to the Republican brand, the GOP’s response is more concerning because it undermines independent legislative oversight of the executive branch. We need a real investigation into the IRS–one that is focused on protecting our rights, not pursuing a political vendetta against Holder or Obama. That is difficult to achieve, however, when top Republicans issue verdicts before collecting evidence.

The IRS scrutiny of political activists could turn out to be one of the most serious First Amendment violations in the federal government today. If citizens’ speech rights were violated by the government, that is a serious problem even if the president was not involved. That is the scandal and the legal priority: Our government must strenuously avoid viewpoint discrimination in the regulation of democratic activity–even just a hint of it, and even if it’s “only” caused by incompetence (rather than orchestrated bullying). That is the substantive concern, of course, and not whether the infraction can be exploited for some pre-cooked political attack.

So far, it doesn’t look like Issa’s committee will apply those priorities in its oversight. Instead, many House Republicans seem to think they’ve found another Watergate. For all the references to that trauma in American government, today’s Republicans have clearly missed a key feature of Congressional oversight during that period.

The Senate special committee on Watergate, which convened hearings which transfixed the nation, was careful to pursue a nonpartisan search for the facts. It was a Republican member, Howard Baker, who posed the canonical question about what the president knew, and when he knew it. And it was Republicans on the House Judiciary Committee–six of them–who delivered the key votes to advance Articles of Impeachment against their own party’s president. It was a model of independent and patriotic oversight, not petty politics.

That is another reason why today’s disputes are the furthest thing from Watergate–there is no evidence of crimes emanating from the White House, and very few signs of a Republican Party capable of conducting nonpartisan oversight in the Congress.