When Big Oil companies invest in something, they expect a good return -- and they've been investing in New Mexico Congresswoman Heather Wilson for years. Wilson's received more than $740,000 from oil and gas companies for one reason: She keeps paying dividends.

Take a look at her record. She's voted to kill investments in clean energy. She's voted to keep doling out billions in tax handouts to BP, Exxon, and Shell. And she's voted to let her Big Oil campaign contributors off the hook for contaminating the water supplies used by tens of thousands of New Mexicans with toxic MTBE chemicals.

Now that Wilson is running for U.S. Senate, a coalition of environmental groups has joined together to make sure voters know about her dangerous record. The Sierra Club recently began airing this ad, highlighting that Wilson voted multiple times to protect the oil and gas companies that endangered New Mexico kids by contaminating our water with toxic MTBE chemicals. And the ad notes that Wilson's votes came after she'd taken tens of thousands of dollars from the very oil and gas companies threatened with lawsuits for their reckless activities.

Big Oil polluted, Big Oil paid, and Wilson let them off the hook. It's a pretty straightforward case of another politician bought and paid for by billionaire Big Oil executives -- and because they've already put so much money toward keeping her in office, Big Oil and its allies are scrambling to protect their investment.

The shadowy, right-wing groups defending Wilson are trying to cover their tracks, but their oil-soaked footprints reveal their links to the dirty energy industry. The U.S. Chamber of Commerce, which -- like Wilson -- counts ExxonMobil as a financier, is airing an ad praising Wilson for supporting the very same policies Exxon demands. Meanwhile, Karl Rove's shadowy, oil-backed "American Crossroads" has the gall to declare Wilson an "independent voice."

The latest to defend Wilson is the National Republican Senatorial Committee (NRSC), a group that's taken $3.8 million from oil and gas companies since 2010. The NRSC recently criticized the ad and echoed Wilson's talking points.

In reality, the facts are simple and we invite anyone to check them:

• Hundreds of groundwater sites in New Mexico have been contaminated, including entire water systems serving tens of thousands of New Mexicans and locations particularly threatening to our kids, like an elementary school in Edgewood.

• Heather Wilson voted not once, not twice, not three times but four times to let her big polluting campaign contributors off the hook for polluting New Mexico's water with chemicals that may cause cancer in kids. She not only voted for energy legislation in 2003, 2004, and 2005 that included a provision shielding MTBE producers from liability for contaminating water but also voted against legislation that would have stripped that provision from the law.

New Mexico voters deserve to know the truth about Wilson's record, but big polluters and its allies are desperate to hide that truth in order to protect their investments in politicians and their record profits. 

Their largesse may buy them airtime, but their defense of Wilson amounts to nothing more than Big Oil declaring Big Oil's favorite candidate to be right about Big Oil. That's not news -- just more politics as usual. 

--David Farrell, Sierra Club Political Chair for the Southern Group, Rio Grande Chapter