Darrell Issa and Elijah Cummings, House Oversight Committee chairman and ranking Democrat, respectively, aren’t exactly known for their intra-party camaraderie, especially seeing as how Cummings has continually derided the ongoing investigation into the IRS’s scandalous targeting of conservative groups as nothing more than a hyper-partisan fishing expedition — but this just got real.

Funnily enough, just this morning Cummings’ office released a report that seems to focus mainly on comparing Issa’s investigative activities to those of the late Sen. Joe McCarthy as a similarly “disgraceful stain on our nation’s history”:

As Issa, a California Republican and the Oversight chairman, pushes for former IRS official Lois Lerner to be held in contempt for invoking her Fifth Amendment rights not to testify before the committee, Cummings’s office is releasing research Wednesday showing the majority of the previous times Congress took such a step were during McCarthy’s investigations.

“We oppose Chairman Issa’s efforts to recreate the Oversight Committee in Joe McCarthy’s image, and we reject his attempts to drag us back to that shameful era in which Congress tried to strip away the constitutional rights of American citizens under the bright lights of hearings that had nothing to do with responsible oversight and everything to do with the most dishonorable kind of partisan politics,” said the report for committee Democrats, which was released early to POLITICO Pro Tax.

Yes, most original. This afternoon, however, Issa sent a letter over to Cummings’ office containing some distinct questions about emails revealing Cummings’ past communications with the IRS, raising “concerns that that the IRS improperly shared protected taxpayer information with [Cummings’] staff” which “surreptitiously” coordinated with the agency to request that information, specifically about conservative organization True the Vote. Issa’s letter makes for some well-timelined and skim-able reading, and here’s NRO‘s summary:

E-mails unearthed in the course of Issa’s investigation into the IRS’ inappropriate targeting of right-leaning groups show that in August 2012, a member of Cummings’s staff contacted the IRS asking for any publicly available information on True the Vote. The matter was discussed by IRS officials including Lois Lerner, the former exempt organizations chief who retired in the wake of the targeting scandal. and one of Lerner’s deputies, Holly Paz, subsequently sent the organization’s 990 forms to Cummings and his staff. The correspondence does not indicate, however, whether the action the IRS took with relation to True the Vote was prompted by the request from Cummings’s office.

Nonetheless, Engelbrecht’s True the Vote received a letter from the IRS with inquiries that agency officials have testified were unprecedented in its scope. Cummings’s letter contained questions that closely mirrored those posed by the IRS, and Issa details them in his letter, strongly implying that one was modeled on the other.

Oh, snap. As Issa noted in his letter, Cummings has previously denied that his office “made any inquiries to the IRS” that “may have led to additional scrutiny,” and Issa just extended a very public invitation for Cummings to explain himself. In the meantime, the Lerner contempt vote is scheduled for tomorrow.