The most cynical explanation of money in politics is that campaign contributions are basically bribery, in which donors pay politicians for beneficial policies. This, I believe, is rarely the case.

The most innocent explanation is that donors give money to politicians who believe in what the donors support. This is often true, but too innocent.

The most accurate explanation, I think, is that donors buy access with donations. That access means they get their voices heard. Even positing that lawmakers vote their conscience, this access game tilts the playing in favor of those who donate.

My access explanation is neither original nor controversial. But still, it's nice to get some scientific support for the notion that money buys access.

The Washington Post's Matea Gold reported on a new study:

Last summer, a group of CREDO fellows e-mailed congressional offices seeking meetings to discuss the measure, sending one of two different form letters.

The first e-mail ... said that about a dozen CREDO members “who are active political donors” were interested in meeting with the member of Congress. ...

The second e-mail stripped out the donor references and instead said “local constituents” were looking to meet the member of Congress. ...

The results: Only 2.4 percent of the offices made the member of Congress or chief of staff available when they believed those attending were just constituents, but 12.5 percent did when they were told the attendees were political donors.

Gold infers that all these emails were to Democratic Congressmen. I imagine results would be similar for Republicans.

The samples are too small, but I wonder how things break down along axes. Are vulnerable members more susceptible to donor pressure? Is their variance along the spectrum from center to Left?