The U.S. Chamber of Commerce has stepped up its defense of Senate Minority Leader Mitch McConnell (R-KY) with a new television ad praising his efforts on behalf of the coal industry.

The ad, titled “Mitch McConnell — Fighting Hard for Kentucky Coal,” hit the airwaves on Tuesday.

“Coal means jobs in Kentucky,” the ad’s narrator says. “While the EPA and bureaucrats try to kill Kentucky’s coal industry, Mitch McConnell is fighting back, fighting hard, opposing regulations on coal, working to block the EPA and shut down the bureaucrats.”

The ad buy, which reportedly cost the Chamber of Commerce $182,240, is the lobbying group’s latest attempt to push back against Tea Party candidates like McConnell’s primary opponent, Louisville businessman Matt Bevin. Earlier this year, the Chamber enthusiastically backed Alabama Republican Bradley Byrne in his successful congressional campaign against far-right challenger Dean Young.

All three of the top candidates in the Kentucky Senate race have tried to cast themselves as defenders of the coal industry. McConnell frequently touts his strong record on coal, while Bevin has criticized the five-term incumbent for his vote in favor of the 1990 Clean Air Act. Democrat Alison Lundergan Grimes — who received the endorsement of the United Mine Workers of America on the way to winning her campaign for secretary of state in 2011 — has criticized McConnell for not adequately supporting the Coal Healthcare and Pensions Protection Act of 2013, which is currently being debated in the U.S. House of Representatives. Grimes has also said that she is “deeply” disappointed in the Obama administration’s proposed regulations on coal-fired power plants, and accused them of taking “direct aim at Kentucky jobs.”

There is reason to doubt that the “war on coal” — which has been drastically exaggerated — is actually an effective wedge issue. Mitt Romney’s relentless attacks on President Obama’s coal policies failed to flip coal-rich swing states like Ohio, Pennsylvania, and Virginia to the Republican column in 2012, and even National Mining Association spokesman Luke Popovich has since acknowledged that the “‘war on coal’ never resonated with much conviction among ordinary Americans.”

Early polling of the race suggests that McConnell holds a comfortable lead over Bevin in the Republican primary, but is running virtually even with Grimes.