Sen. Lamar Alexander (R-Tenn.) doesn’t see a contradiction between his position against repealing an Environmental Protection Agency air-quality rule and the message Republicans have been sounding that EPA rules are hurting small businesses.

“I think we in the Republican Party are grown-up enough to separate a whole avalanche of awful rules, many of which we have seen from the EPA, from good rules, which are rules that make our air clean,” Alexander said Tuesday.

“Most of my constituents where I live and breathe the air are Republicans,” he continued. “They are all for clear air.”

As Senate Republican Conference chairman, Alexander is supposed to be in charge of the party’s public relations efforts. But on the clean air rules, he is decidedly off-message — an indication that he’s not waiting until he vacates his leadership post in January to strike out on the independent path he vowed to pursue once he steps down.

Alexander announced Monday evening in a stinging press release that he will vote against fellow Republican Sen. Rand Paul’s (Ky.) bill to repeal an EPA clean air rule designed to limit power-plant pollution blowing across state lines. “Tennesseans admire much about our Kentucky neighbors — their bluegrass, basketball and distinguished United States Senators,” Alexander said in the statement. “But we don’t want Kentucky’s state income tax. And we don’t want Kentucky’s dirty air.”

Alexander’s position also pits him against a fellow GOP leader and friend, Minority Leader Mitch McConnell (Ky.), who is supporting Paul’s proposal.

The vote on a resolution of disapproval — likely to occur Thursday — will mark the first time that Alexander will vote against McConnell on a high-profile issue since he announced in September that he would leave his post as the No. 3 Senate Republican.

According to Paul’s office, the Kentuckian is seeking to prevent the implementation of this new rule because he believes it creates unnecessary regulation in an area that has been properly controlled by previous regulations. The EPA estimates this rule will cost close to $2.4 billion annually, which includes the $1.6 billion already being spent to comply with the previous rule.

Alexander is introducing legislation that would enact the proposed rule into law but give utilities one additional year to implement it. 

A GOP leadership aide said leaders do not see Alexander’s position as muddying their message on federal regulations.

“There is broad Republican unity that most federal regulations are standing in the way of job creation,” the aide said.

Sen. John Cornyn (Texas), who heads the National Republican Senatorial Committee, said he believes there is room for debate on the issue within the party.

“We all agree with the goal, and that is clean air,” said Cornyn, who plans to back Paul. “The question is what additional burden are we going to put on the states and businesses we are depending on to create jobs.”

A Senate Democratic leadership aide said the Paul proposal is not a serious bill and that it is expected to fail. The measure needs 51 votes to pass.

“If Republicans are going to put stunt, message votes on the floor, they should have their caucus in line,” the Democratic aide said.

The White House also opposes the Paul measure and threatened to veto the proposal Tuesday if it reaches the president’s desk.

Alexander, who has long had a reputation for being environmentally conscious and who famously drives an all-electric Nissan Leaf, waved off questions about whether energy issues were one reason he decided to leave leadership.

“I support the clean air rule because I live and breathe in the shadow of the Great Smoky Mountains, where the local Chamber of Commerce’s No. 1 objective is clean air,” he said. “We don’t want the Great Smoky Mountains to be called the Great Smoggy Mountains. We don’t want our infants to be sicker, and we want to get our Volkswagen [car manufacturers] suppliers, and they all are going to need a clean air permit. I have been introducing clean air regulation every year since I’ve been in the Senate.”

But looking at Alexander’s comments from September, it’s not hard to see that he had concerns about being able to push for issues that may not have been on the agenda for GOP leadership.

“Stepping down will liberate me to work for results on the issues I care the most about,” Alexander said at the time.

A GOP aide said that Alexander believes he can help the Senate as a whole, where partisanship has stalled most bills, to get back to legislating.

“Alexander thinks he can better help the Senate achieve results by spending his time working outside leadership with Senators from both parties,” the aide said.

The aide added, “Senators are here to get things done, so there’s a great pent-up energy that could be channeled into some truly bipartisan agreements.”

Other Republicans could also oppose the Paul proposal, particularly those from the Northeast, according to a Senate GOP aide, who said that the issue is more regional  than ideological.