Nate Silver from FiveThirtyEight.com has written an interesting statistical analysis of money in politics as it relates to the current debate on health care reform and the popular public option.
"What happens if we set the lobbying variable to zero for all senators? That is, suppose that the health care insurance industry were prohibited from making political contributions? In that case, the model predicts, 47 senators would currently support the public option, as opposed to the 38 who actually do. In other words, the insurance industry's influence appears to swing about 9 votes against the public option. Whatever number of senators wind up supporting the public option, add 9 to it, and you'll have a decent ballpark estimate for what the level of support might be if not for insurance industry contributions."
"...To be clear, not all of the opposition to the public option is the result of special interest money. Most Republicans probably oppose it on general principle, and there are a couple of Democrats, like Maria Cantwell of Washington, who have yet to come around to it even though they've taken almost nothing (in Cantwell's case, literally nothing) from the insurance industry. But the money is why, even with 59-60 votes in the Senate and a President with high approval ratings, Democrats are facing an uphill battle on the issue."