Issa tangled with IRS Commissioner John Koskinen, peppering him with demands to turn over all of the emails from Lois Lerner and five other IRS employees at the center of the scandal that began last year.
"Unfortunately, you've been more concerned with managing the political fallout," Issa accused Koskinen in his opening statement.
Lerner has refused to testify before the committee, pleading her Fifth Amendment rights, and Issa has been determined to gain access to all of her email communications, saying emails that might appear to be irrelevant have in the past led to the discovery that Lerner had been discussing targeting tea party groups for extra scrutiny.
The crux of the issue came down to the volume of documents demanded by the committee in subpoena, which Koskinen said would "overwhelm the investigators, not us," if they were required to turn over all of the documents, including those that did not include specific search terms determined by the congressional committees.
"We would not have found Lois Lerner talking to her daughter about overtly partisan and political activity if we had only looked for determination," Issa said.
Koskinen, while warning the resulting flood of documents would be overwhelming, said the IRS team working on the investigation would prioritize sending the Lerner emails that contained relevant search terms, and then move on to the rest.
"With all due respect, we don't care what you think is relevant," said Jim Jordan, R-Ohio.
The commissioner said that, even in responding to the subpoena fully by turning over all of Lerner's emails, the process would still take significant time to go through each document and redact confidential taxpayer information.
"This commissioner has no intention of complying with this duly-issued subpoena," charged a heated Rep. Jason Chaffetz, R-Utah.
"We have never said we won't comply," Koskinen responded. "To respond fully to this subpoena, it's going to take years, not months."