When U.S. Sen. Mary Landrieu became chair of the powerful Energy and Natural Resources Committee, it was hard to envision a downside for her and her tough reelection bid. The new post played to her strengths, from her seniority to her advocacy for a vital local industry. What could go wrong?

A few months and several major policy skirmishes later, the answer to that question is clear. Landrieu’s chairmanship positions her as a champion of oil and gas. But it also casts a spotlight on the outer limits of her power, and the distance between Landrieu and the Democratic leadership on key issues. So while she’s talking about the new gig every chance she gets, so are the people who want her tenure to be short-lived.

It’s hardly happenstance that both Landrieu and U.S. Rep. Bill Cassidy, her main GOP challenger this fall, recently visited energy facilities. Landrieu’s trip to NRG Energy’s Big Cajun II power plant in New Roads was official business, while Cassidy’s journey to New Industries in Morgan City, which services offshore facilities, was a campaign stop, although those lines get blurry this close to an election. The visits took place a week apart, and the candidates didn’t cross paths. Still, their comments to workers and in press interviews afterwards are the closest we’ll get to a debate at this early stage, so consider it something of a preview of the next five months.

Landrieu talked of the power of the gavel, which, she said repeatedly, belongs not to her but to her constituents. She said the last energy chair from Louisiana, J. Bennett Johnston, used it to help launch the offshore industry and deregulate pipelines. Landrieu also stressed her support for the stalled Keystone XL pipeline, and her opposition to the new EPA emission standards that the Obama administration had just handed down. She said her top goal is to make North America energy independent.

“So when people say to me, ‘Senator, does it make a difference who holds the gavel? Does it make a difference if it’s a senator from a state that believes in domestic energy production, truly all of the above? Does it make a difference that a senator understands the importance of oil, gas and coal, using it in a responsible way?’ I’d say absolutely yes,” she said. “And the evidence is, when you see what chairmen have done either in the right direction or in the wrong direction.”

Cassidy begged to differ. While he gave Landrieu credit for her rhetoric and, a bit grudgingly, for her voting record, he argued that the key variable is which party controls the chamber.

“In Washington … the Republican Party is all about oil and gas jobs and everything that goes with it, and the Democratic Party’s not,” he said. “That’s not true of us here in Louisiana, but it is true up there. The only way you stop those regulations is if the Republicans have the House and Senate, and then we can pass some legislation that says, ‘EPA, you can’t do this.’ ”

Asked about that sort of criticism, Landrieu insisted there’s plenty she can do, from continuing to push for a vote on Keystone — “I have every intention of getting that passed” — to advocating for a better revenue sharing deal to voting against the Obama emission standards.

“It takes 60 votes in the Senate to pass anything, so with my vote we’ll need 59 others,” she said. “But my vote’s there.”

To Cassidy, though, Landrieu’s failure to get Keystone approved and her affiliated PAC’s prolific contributions to other Democrats are damning.

“The reason we can’t get that vote in the Senate on Keystone is in part because she supported the people who won’t allow it to happen,” he said.

On related matters, the two leading candidates differed by degree. Both noted that many plants — including Cajun II, which is partially converting from coal to natural gas — are reducing emissions on their own. Rather than regulation by “unelected bureaucrats,” Landrieu pitched legislation that “sets very clear targets with as much flexibility as possible but with the aspiration in mind of energy independence, security, reliability and affordability.” Cassidy suggested that the “normal regulatory and market-based approach” is both sufficient and already working.

Landrieu said fighting climate change should be one of many considerations in setting energy policy.

“I am not a climate change denier,” she said. “I know that carbon is having an effect on our atmosphere, but I also most certainly know that we can do this the smart and right way to make sure we protect jobs and not shut down plants all over America.”

Cassidy didn’t deny it’s a problem, but he also made it perfectly clear that it’s not a priority, and that he doesn’t believe the emissions standards would help, anyway.

“There’s one party that wants to promote oil and gas, and our using our own natural resources to create better jobs with better benefits for working Americans,” he told workers at the Morgan City plant, “and the other party is so hung up on climate change that they are willing to kill these jobs, the jobs that you have, in order to save the world.”

Stephanie Grace can be contacted at sgrace@theadvocate.com. Read her blog at http://blogs.theadvocate.com/gracenotes. Follow her on Twitter @stephgracenola.