Former Michigan Secretary of State Terri Lynn Land (R) has two new ads slamming Rep. Gary PetersGary Charles PetersGOP tax bill has transportation advocates scrambling GOP tax bill ends electric vehicle tax credit, overhauls other energy taxes Cities grapple with how to protect soft targets from new attacks MORE (D-Mich.) for opposing the Keystone XL pipeline and tie him to billionaire environmentalist Tom Steyer.

"Steyer could make millions by stopping the Keystone pipeline, and Peters stood with Steyer, voted against energy independence, killing jobs, increasing oil and gas prices. Gary Peters: Working for billionaires, not Michigan," one of the ads says.

The ads mirror those Peters and his allies have run attacking Land for the support she's received from the billionaires Charles and David Koch's Americans for Prosperity.

The ads don't explain how Steyer could profit by blocking the pipeline, though one says he "could make millions by killing the pipeline from investments in Keystone's competitor."

Land's campaign says Steyer might be invested in natural gas or green energy products that could go up in value if Keystone is blocked.

A poll conducted for a pro-Keystone XL group released on Wednesday found Peters ahead in the race by 42 percent to 35 percent, though it also found that opposing Keystone could hurt him in the race.

— This post was updated at 12:37 p.m.