Sen. Mary Landrieu of Louisiana, who’s seeking reelection for a third term, is the only Democrat to make the League of Conservation Voters’ “Dirty Dozen” list this year. LCV has given her a lifetime score of 44 percent and says she’s “the worst Democrat in the Senate on environmental issues currently running for reelection.”

Environmentalists are particularly critical of Landrieu for supporting the oil and gas industry, one of the major industries in her home state. “She acts more to protect Big Oil than the future for the people of Louisiana,” said Tony Massaro, LCV’s senior vice president for political affairs and public education.

Landrieu’s campaign website proudly quotes a recent piece in the Baton Rouge Advocate that called her “the most-fervent pro-drilling Democrat in the Senate.” Her site lists “energy independence” as one of her key issues, claiming that “Senator Landrieu led efforts to expand the reach of Louisiana’s oil and gas industry to move the nation towards independence from foreign oil and reduce the cost of gasoline.”

She’s voted repeatedly to keep subsidies in place for Big Oil, including a “no” vote last year on a package that would have repealed tax breaks for the oil industry and invested the savings in cleaner sources of energy. A “yes” vote from her would have meant passage of the provision; the New York Times editorial board labeled her a “villain” for breaking with her party and ensuring the provision’s defeat.

Landrieu regularly touts her work to promote more offshore drilling. This summer, she was a member of the so-called ”Gang of 20″, a bipartisan group of senators sponsoring legislation that combined investments in renewables with plans to open nearly 120 million new offshore acres to drilling.

In 2006, Landrieu teamed up with Sen. Pete Domenici (R-N.M.) to successfully push through the “Gulf of Mexico Energy Security Act,” which opened 8.3 million acres of the Gulf Coast for drilling. It was the first time in a quarter of a century that a portion of the outer continental shelf had been opened to energy exploration. Also that year, she introduced the “Gulf Coast Protection Act,” which would have channeled some offshore oil and gas revenues to wetlands restoration and hurricane protection, but also would have allowed some of the funds to be used for onshore drilling infrastructure, which didn’t please enviros.

On the campaign trail, Landrieu calls for coastal restoration measures and talks up her work to get funding for them from oil and gas revenues. She worked to secure $540 million in coastal impact assistance for Louisiana over four years, to be used by communities affected by coastal drilling.

While her affection for the oil industry evokes no love from enviros, it has brought in $307,950 in campaign donations from the oil and gas sector this election cycle, and $666,994 over her career.

That’s not to say her challenger this year, John Kennedy (an unfortunate name for a Republican, no?), isn’t a friend of the oil industry as well. The current state treasurer has raised $135,900 from the oil and gas sectors for this race, and his energy plan pushes heavily on the “more drilling” message.

“America must become energy independent,” Kennedy declares on his campaign website. He calls for “increased oil exploration in the Outer Continental Shelf (OCS), ANWR, oil shale reserves and tar sands,” as well as “clean energy technologies, such as nuclear power, renewable sources, ethanol, coal, biodiesel, solar and wind.”

Kennedy and the Republican Party have been critical of Landrieu for not being pro-oil enough, citing among other things her vote against advancing oil-shale production in Western states. A Kennedy campaign ad criticizes her on this, and ends with the line, “I’m John Kennedy, I’m for drilling everywhere, and I approve this message.”

Kennedy also stresses the importance of protecting Louisiana’s coastlines, and says the state needs a much larger share of OCS oil and gas revenues so it will have more money to spend on restoration projects.

Landrieu’s seat is one of the few Republicans see as vulnerable this year, which has prompted the party to concentrate a lot of their efforts on the state. Or at least they were until about a week and a half ago, when the National Republican Senatorial Committee pulled their television advertising in the state, a sign that they no longer hold onto much hope of taking the seat. A recent poll shows Landrieu leading by about 10 points.

But no matter who wins, enviros won’t be rejoicing.