U.S. Senate Minority Leader Mitch McConnell of Kentucky and Sens. Rand Paul of Kentucky, Ted Cruz of Texas and Mike Lee of Utah will join U.S. Rep. Michele Bachmann this morning at a press conference on Capitol Hill to discuss the Internal Revenue Service targeting of tea party and other conservative groups seeking tax-exempt status.

Bachmann, chairwoman of the House Tea Party Caucus, has called the targeting "outrageous" and a "stunning abuse of power."

The tax scandal has served as a rallying point for the tea party, which began in 2009 as an anti-tax movement, but lost steam during the last election cycle. Tea party leaders from across the country and more than 20 Republican House members also plan to attend the event.

IRS leaders issued an apology last week for singling out organizations with the words "tea party" and "patriot" in their applications for extra scrutiny, stalling the approval process.

With political pressure mounting, President Obama announced Thursday that acting director Steven T. Miller will leave the tax agency next month.

The tax scandal has served as a rallying point for the tea party, which began in 2009 as an anti-tax moment, but lost steam during the last election cycle.