DRILLING IN LAKE MICHIGAN FOR OIL…. If one were to categorize degrees of extremism in statewide candidates this year, it’s probably fair to characterize Nevada’s Sharron Angle and Kentucky’s Rand Paul as the most radical. The second tier, though, includes some real doozies, including Colorado’s Ken Buck, Florida’s Marco Rubio, and Pennsylvania’s Pat Toomey.

By any reasonable measure, Wisconsin’s Ron Johnson, Sen. Russ Feingold’s (D) Republican opponent, belongs in the same group. Today, Feingold is launching an ad that tells voters, “I said no to drilling in our Great Lakes, but one opponent, Ron Johnson, disagrees. He’s willing to hand over the Great Lakes to the oil companies — threatening Wisconsin’s economy, and a way of life for generations of Wisconsin families. We won’t let that happen.”

At first blush, this seems implausible. Ron Johnson has repeatedly sided with oil companies since launching his Senate campaign, but would he really consider drilling in the Great Lakes?

Actually, yes, and the closer one looks at this, the uglier the story gets.

Republican U.S. Senate candidate Ron Johnson found himself under the political microscope late last week after it was revealed that he owns up to $315,000 in BP stock while he has defended the oil giant against its critics and called for continued offshore drilling. […]

Johnson, whom national Democrats like to refer to as the “forgotten Tea Party candidate,” has expressed disappointment with the administration’s “assault” on BP. At the same time, he’s been a vocal advocate for continued and even accelerated oil and gas exploration, going so far as to express an openness to drilling in the Great Lakes.

According to Johnson’s financial disclosure reports, the far-right candidate owns as much as $466,000 in oil company stocks, including as much as $315,000 in BP alone.

Johnson hasn’t mentioned he has a considerable financial stake in BP’s future while he’s run around Wisconsin defending BP and the oil industry, and suggesting these same companies get drilling rights to the Great Lakes.

Polls suggest Feingold is vulnerable this year, but Johnson’s extremism may yet prove to be a tough sell in a traditionally Democratic state. The image of a Deepwater Horizon rig in Lake Michigan may be hard for mainstream voters to shake.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.