My recollection of this is that the disagreement between the IRS and the Republican Party had nothing to do with the "gift Tax". My understanding is that the IRS concluded that these political PACS, both Liberal and Conservative, did not qualify under the section of IRS code they were seeking status under, because in the opinion of the IRS they were not bonafide "Social Welfare Organizations", but rather section 527, tax exempt, political organizations. Under section 527 their donors names would have to be revealed. This was the crux of the issue: Whether or not the donors names would be revealed, and that had to do with what section of the code they were allowed to file under. The issue was further muddied by the ratio of conservative to liberal political organizations attempting to file as social welfare organizations, being roughly 30 to 1. This made it appear as though the the IRS was "targeting" conservative "social welfare organizations" since the ratio of IRS investigations of these phoney social welfare organizations was heavily skewed toward the conservative groups.
(Of course the IRS, in their inimitable fashion, thoroughly fucked things up by pre-qualifying some organizations on the basis of trumped-up estimates of how the organizations revenues would be spent. These estimates, after the election!, turned out to be wildly wrong. On top of that the IRS had a political zealot, as it turned out, in charge of the IRS office that was to determine under what section of code these organizations qualified. The investigation quickly deteriorated into mud slinging and wild accusations, and veered off into questions of whether the chief witness, the political zealot, Louis Lerner, should be held in contempt. Nothing was ever settled, but politicians on both sides used the opportunity to grandstand on television. The IRS subsequently reviewed their procedure for qualifying organizations for social welfare status, and has revisited those sections of the code under question.)