Republican Sen. Thad Cochran launched a new TV ad Tuesday touting both a conservative record and a history of “standing up for Mississippi.”  

It’s the fourth ad in the past month from the six-term incumbent, who faces his toughest race in 30 years from a tea party-backed primary challenger, state Sen. Chris McDaniel. This is arguably the most competitive primary any Senate Republican is facing this cycle.  

The new ad, which is running statewide, attempts to undercut the attack line by McDaniel — and the conservative outside groups supporting him — that Cochran’s track record over 35 years is not conservative enough. The primary is June 3. www.youtube.com/watch?v=1lizrWM9JA0  

“Only one candidate for U.S. Senate has been endorsed by the National Rifle Association,” the ad’s announcer says. “Only one candidate has voted against Obamacare more than 100 times. Only candidate has been endorsed by Governor Phil Bryant. And only one candidate has a 100 percent pro-life voting record from National Right to Life.”  

McDaniel has not yet aired a TV ad, but he’s received help on the airwaves from the Club for Growth and Senate Conservatives Fund. Madison Project, which supports conservative candidates, including McDaniel, responded to the ad by saying Cochran “is campaigning as a born-again conservative.”  

Cochran has an ally in the Mississippi Conservatives super PAC, which recently ran an ad criticizing McDaniel’s hesitation about whether he would have sought federal funding for Hurricane Katrina disaster relief.  

The winner will likely face former Rep. Travis Childers, a Democrat, in the general election. The race is currently rated Safe Republican by Rothenberg Political Report/Roll Call.