The contentious battle for the Republican nomination in Mississippi's Senate race is now playing out in earnest on television, with three new ads released Monday hitting both incumbent Sen. Thad Cochran and his opponent, Chris McDaniel.

In a year that has produced remarkably few serious challenges to Republican senators by Tea Party insurgents, the Mississippi match-up has emerged as a high-profile counter-example to the trend and a serious threat to Cochran's five-decade career in Congress. Smelling blood, conservative outside groups have swarmed to support McDaniel.

To fight back, Cochran's campaign has begun to air an ad hitting McDaniel for waffling on whether he would have supported Hurricane Katrina relief funding.

"If Chris McDaniel won't do anything for Mississippi," a male narrator asks, "why should Mississippians do anything for Chris McDaniel?"

The attack ad is an unfamiliar exercise for Cochran, who hasn't flexed his campaign muscles since he faced a competitive challenge from Democratic Gov. William Winter in 1984, three decades ago. Cochran won the race handily.

Public polling on the match-up between Cochran and McDaniel so far has been scarce and inconsistent, with most surveys showing Cochran leading McDaniel by at least low double-digits — but not out of striking range, particularly should the primary election attract low voter turnout.

Plus, McDaniel is receiving aid from powerful allies, including the conservative and cash-rich Club for Growth, which on Monday unveiled an ad sampling five decades of Cochran's votes that might be unpalatable to conservative Republicans, including a recent one to raise the debt limit.

"Thad Cochran: Five decades in Washington is enough," the ad concludes.

Senate Conservatives Action is also in the mix, and the third-party group released a positive spot for McDaniel on Monday showing him delivering a speech to supporters.

"We will not compromise on the United States Constitution," McDaniel says in the ad.

The primary race will be held June 3. Democrats, meanwhile, have scored a competitive recruit in former Rep. Travis Childers, D-Miss.