Before Sarah Palin’s VP nomination acceptance speech tonight, the McCain campaign released a new ad, “Alaska Maverick.” It compares Palin to Democratic presidential candidate Barack Obama: “She has a record of bi-partisan reform,” it says. “He’s the Senate’s ‘most liberal.'”

“She took on the oil producers,” it continues. “He gave big oil billions in subsidies and giveaways.”

The accusation that Obama “gave big oil billions in subsidies and giveaways” is somewhat misleading. The McCain campaign is referring to his vote on the 2005 energy bill, a sweeping, oil-friendly piece of legislation that enviros largely opposed. Obama voted for it, citing its support for ethanol and “clean coal” technology.

McCain voted against the bill, but not because he opposed the giveaways to Big Oil, which is what the new ad would have you believe. His chief criticisms were that he thought it would raise gas prices in Arizona, it mandated too much ethanol use, and its tax incentives for people who buy alternative-fuel vehicles were too generous. According to FactCheck.org, the bill actually “resulted in a small net tax increase on oil companies.”

McCain’s proposed policies would continue subsidies for Big Oil. He supports perpetuating current subsidies, which would total $33 billion [PDF] in the next five years. His plans would also cut taxes on oil companies by $4 billion, according to a recent report [PDF] by the Center for American Progress Action Fund. He also opposes Obama’s plan to impose a windfall profits tax on oil companies.

As for the claims about Palin taking on Big Oil, there is definitely some truth. As Alaska governor, she’s supported a windfall profits tax much like the one Obama has proposed, and last year she pushed through a big tax increase on oil companies. She’s even offered a bit of praise for Obama’s energy plan. She’s also taken on the oil industry over political corruption and the terms of a plan to build a trans-Alaska natural gas pipeline.

But at the same time, she’s a staunch supporter of the industry, touting her state’s “mutually beneficial relationships with the oil industry.” She’s a strong advocate of opening up more areas for drilling, including the outer continental shelf and the Arctic National Wildlife Refuge, and she’s criticized the Bush administration for not being pro-drilling enough.

So overall, the ad’s a mixed bag on truthfulness. Watch it: