The ongoing scandal over IRS targeting of conservative groups has given new life to efforts to eliminate the agency altogether.
The Repeal 16 group created the spot from remarks in recent congressional hearings into two years' worth of missing emails from top IRS officials.
Throughout the hearings, Koskinen maintained his organization had done nothing wrong. "I don't think an apology is owed," he said.
The Repeal 16 ad contrasts Republican criticism of Koskinen with Democratic apologies. "Some demand accountability ..." the ad states, "... others cover for corruption."
A number of notable Democrats defended Koskinen during the hearings, including Rep. John Lewis, D-Ga., and Rep. Gerry Connolly, D-Va., who are featured in the ad.
Rep. Elijah Cummings, D-Md., delivered a particularly theatrical apology to Koskinen. "I thank you from the depths of my heart for taking on this task. I cannot begin to tell you how pained I feel listening to all of this," he said, referring to Republicans' sharp criticism of IRS behavior.
"The apology that ought to be given is to the American taxpayer," Rep. Paul Ryan noted at a different hearing.
The Repeal 16 ad capitalizes on public skepticism of the IRS's alibi. A Fox News telephone poll conducted June 21-23 found that 76 percent of respondents believe the emails were deliberately, not accidentally, destroyed.