Calling an investigation "tainted" by partisanship goes back at least to the Greeks, but I can't help but be reminded of similar GOP efforts to shoot the investigators.  Two seconds of googling brought up this gem from Tom Delay's spokesman:

This purely political investigation has been marked by illegal grand jury leaks, a fundraising speech by Ronnie Earle for Texas Democrats that inappropriately focused on the investigation, misuse of his office for partisan purposes, and extortion of money for Earle's pet projects from corporations in exchange for dismissing indictments he brought against them.

Ronnie Earle's previous misuse of his office has resulted in failed prosecutions and we trust his partisan grandstanding will strike out again, as it should.

How did things work out for the GOP Majority Leader?  In any case, I'm sure there are plenty of other examples of GOP knuckleheads blaming partisan attack dogs, even when the investigation efforts are bipartisan, as with the former Miss Congeniality of Alaksa.  I leave it to the AP:

The lawsuit called the investigation "unlawful, biased, partial and partisan." None of the lawmakers who filed the suit in Anchorage Superior Court serves on the bipartisan Legislative Council that unanimously approved the investigation.