Sen. Angus King, I-Maine, is teaming up with Sen. Tom Coburn, R-Okla., in a push to strip the National Football League of its tax-exempt status.

King announced Wednesday he's co-sponsoring Coburn's Properly Reducing Overexemptions for Sports Act, which would affect the NFL and other wealthy professional sports leagues currently enjoying 501(c)(6) tax-exempt status.

King, a former governor who caucuses with Democrats, is the bill's first co-sponsor and now he's helping recruit more ahead of Sunday's Super Bowl game.

"For every dollar that goes out in a case like this, that's a dollar my constituents have to pay in income taxes," King tells U.S. News. "When I talk to people about the NFL being a non-profit tax-exempt organization they're just astounded."

Several senators seem sympathetic to the bill, King says, and he believes the proposal stands a good shot at become law – although he considers it possible a larger tax policy bill will envelop it.

In a letter to colleagues this week, Coburn and King said the bill would add $10 million a year to federal coffers. Major League Baseball voluntarily abandoned its tax-exempt status in 2007, the letter says, but the PGA Tour and the National Hockey League continue to avail themselves of the tax break.

The PRO Sports Act would specifically bar professional sports organizations with annual revenues of more than $10 million from 501(c)(6) status. That section of the tax code is intended to assist trade groups.

Among the reasons King decided to join Coburn is the sky-high salary of NFL Commissioner Roger Goodell, who was paid nearly $30 million in 2011, according to non-profit tax filings.

"I wouldn't be honest if I said that didn't [motivate me]," King says. "It's hard to say an organization that pays its executive director $30 million and yet is a tax-exempt entity – its hard to look my constituents in the eye and say that's good public policy."

Teams that are members of the NFL do pay taxes, supporters of continued tax-exempt status point out. The leagues then supply the central NFL office with much of its revenue.

"We're not alleging that the whole operation is enjoying a tax break," King says.

Tax returns from 2011 show the NFL received $254 million in membership dues from teams. It paid nearly $108 million in salaries and gave just $2.3 million to charity. Around $2.1 million of the charitable donations went to expanding the Pro Football Hall of Fame in Canton, Ohio.

"I'm a serious NFL fan, I grew up on the NFL and I love the game," King says. "I just think this is an inappropriate use of taxpayers' money."