If you watch TV talking heads shows much you've probably seen Larry Sabato. He's a professor at the University of Virginia and he studies American politics. In 1996 he and Glenn R. Simpson wrote a book called "Dirty Little Secrets-The Persistence of Corruption in American Politics". It's out of print now. What a shame, because I don't know of another popular market book that assembles so much info about corruption in elections and politics in the US.
The book is about 350 pages, with another 70 of reference matter. I can't do it justice in one quick and dirty blog item, but the part that I found the most interesting was about street money.
Sabato notes that "It is no exaggeration to say that the Democrats would almost never win a presidential election, and only occasionally win major elections in many states, without minority Americans." The Dems know it, and spend a fortune to get-out-the-vote (GOTV). Allegedly Douglas Wilder spent $1,000,000 in 1989 to get the vote out in black communities in his successful campaign for governor of Virginia.
Hustlers know the game though, and demand their tribute. Allegedly black ministers and other activists are notorious for insisting on "gifts" or "honoraria" of around $3000-$5000, in return for membership lists, a few phone calls and other non-burdensome services.
The worst excesses supposedly happen in Democratic primaries. As one quote puts it, "Many times people go to both sides and say, 'This campaign has given us money to have donuts for the volunteers and we're going to work hard for them. Now if you give us money for donuts, our people will be too busy eating donuts to go out and work."
Republicans are no angels, and Dems say they catch Republicans paying to suppress minority voting. But as it happens, the most celebrated case was not true. After Christine Todd Whitman's successful campaign in NJ in 1993, consultant Ed Rollins bragged about paying off ministers to suppress the vote. Later investigations concluded that Rollins made this up.
Other Republican stunts include making bids for the black activists, who turn around and shake the Dems down for more yet - this increases the costs to the Dems. Or in SC, state vehicles were tied up with inspections on Election Day so they wouldn't be available for GOTV.
Sabato notes that much of the money supposedly does go to people canvassing voters and driving people to the polls, which is a significant cost (hundreds of "flushers" and "haulers" at $20-$50, plus supervision for every couple dozen or so of those at ~$100 each). The only case of outright vote-buying he cites in the street money chapter dates back to 1888 with Benjamin Harrison, when the going price for "independent" vote was as much as $20 (in 1888 - imagine how much that would be worth today).
There's much more in the book, if you can find it. I enjoyed it, anyway.
UPDATE: Look at what's happening in Maryland.