Elijah Cummings has had enough.

The veteran Maryland congressman’s outburst after his microphone was turned off at a Wednesday hearing on the IRS was out of character for the usually calm Cummings.

But it was part of a larger story: Darrell Issa is perhaps the most-hated member of the GOP by Democrats. The California congressman has used his perch as the head of the House Oversight and Government Reform Committee to lead numerous investigations of controversies of the Obama administration, from the failed “Fast and Furious” gun trafficking program to the IRS’ auditing of tax-exempt political groups.

Issa has had little success in terms of taking on the Obama administration. His investigations have rarely led to information being disclosed that had not already been unearthed by the media. Whatever Obama’s foibles, Issa has found no enduring scandal that has permanently harmed the administration. Issa’s arguably leading target, Attorney General Eric Holder, has survived numerous investigations by Issa and remains in office.

Issa, though, has managed to become a kind of hero to conservatives, a man with both the clout and the will to directly confront Democrats. Turning off Cummings’ microphone in a hearing was only Issa’s most assertive move. He badgered Holder enough in a hearing last year that the attorney general cast Issa’s behavior as “shameful.”