White House press secretary Jay Carney on Thursday said it was “inappropriate” for House Committee on Oversight and Government Reform Chairman Darrell Issa, R-Calif., to abruptly end a hearing, preventing Democratic Rep. Elijah Cummings, D-Md., from speaking.

Carney called Cummings, the top Democrat on the Oversight committee, the “smartest guy in the room.”

Issa and Cummings had a testy exchange on Wednesday during a hearing on the Internal Revenue Service's political targeting of conservative groups seeking tax exempt status.

Issa had called Lois Lerner, the former IRS official in charge of the agency handling tax exemption, but Lerner repeatedly refused to answer his questions.

She pleaded the Fifth Amendment, on the advice of her counsel, leading Issa to end the hearing after 20 minutes, without giving Cummings or other Democrats the chance to speak.

Cummings loudly protested, calling the move “absolutely un-American.”

Democrats say that the investigation into the extra scrutiny of Tea Party groups by the IRS has failed to find evidence that it was directed by senior officials or politically motivated.

But Republicans say that IRS officials have stonewalled their probe and that questions remain about whether the targeting was done to help Democrats in the 2012 election.