The endorsement, from, is a boon to his reelection prospects, as conservatives are still threatening a primary challenge to the senator.

"With the new revelations that the IRS has been targeting Tea Party groups, we need Senator McConnell more than ever. He was sounding the alarm about the government's assault on our First Amendment rights years ago, even when it fell on deaf ears," said Niger Innis, the group's chief strategist.

"We all owe Sen. McConnell a debt for his vision and courage. With support from's hundreds of thousands of supporters and grassroots activists, we are confident that Senator McConnell will be back in Washington next January, fighting on behalf of our Constitution."

McConnell became one of the first lawmakers to call for the resignation of IRS head Stephen Miller on Monday, following the revelation that the IRS had targeted groups with "Tea Party" and "patriot" in their names for extra review.

McConnell, in an interview with National Review, slammed President Obama for setting a "tone" that informed the IRS' actions. And he noted that he had worked to raise awareness about the issue in 2012, when he and a handful of other Republican senators sent a letter to the IRS about alleged similar abuses.

“I cannot resist the temptation to say, ‘I told you so,’” McConnell told National Review.

“I zeroed in on this last summer after reports of this intimidation surfaced in Kentucky and elsewhere. I’ve been warning about this for years," he added.

Tea Party groups in Kentucky have long criticized McConnell, charging that he hasn't done enough to block President Obama's agenda and reduce spending. And McConnell remains one of the least popular senators in the nation, according to a Democratic poll.

But Tea Party activists in Kentucky have yet to front a candidate to challenge McConnell in a primary, and he's made moves in recent years to shore up his support among the conservative base.

The IRS scandal, because it targeted largely Tea Party and other conservative groups, offered McConnell yet another opportunity to do so.