Political contributors to Democratic U.S. Sen. Al Franken and Republican U.S. Rep. Michele Bachmann are mighty giving. First, they donate cash to the nationally known politicians. Then the politicians rent their names and contact data to list brokers. The Minnesotans then pour the profit from the direct-mail companies back into their campaigns.

According to campaign finance documents, Bachmann, a stellar fundraiser, earned more than $425,000 in the past two years through selling and renting her list of donors to third-party companies. Franken, who can light up the left much like Bachmann can the right, brought in nearly $200,000 during that period.

The list income puts the two in the upper echelons of income-making politicians. Only candidates and funds with national reach can bring in the kind of cash for their lists that Bachmann and Franken achieved.

Former presidential candidates and their political action committees -- including 2008 hopefuls John McCain, Hillary Rodham Clinton and Rudy Giuliani, and 2012's Herman Cain -- have also drawn big bucks by sharing information about their donors with direct-mail companies, said Bob Biersack, senior fellow at the Center for Responsive Politics.

Sometimes the cash comes largely in pass-through dollars. A 2011 Roll Call analysis found that McCain's campaign committee made most of its $4.6 million in list-rental income through sharing names with other organizations closely affiliated with McCain's candidacy, including his political action committee.

Those willing to pay for access to the lists hope donors are interested in giving to causes similar to those to which they have given before.

"These are well-educated, politically minded Al Franken for Senate donors. They support his campaign and his positions on protecting seniors, supporting our veterans, environmental protection and increasing available funding for college students" is how California-based Names in the News, which also lists Wellstone Action as a client, describes the Franken list occupants.

Meanwhile, Bachmann's list was valuable enough to the Wisconsin Recall Action Fund that it paid Bachmann's campaign $45,500 to rent the list. The Recall Action Fund opposed the campaign to unseat Republican Gov. Scott Walker.

Profiting from donors' information is a fragile arrangement. Although information about many donors is publicly available in campaign finance disclosure forms, contributors might not cotton to the candidates' profiting from renting out their names. That's why candidates are careful about what kind of users get to have the information.

"Senator Franken occasionally rents out his supporter list, allowing his contributors to hear about other candidates or organizations who share his values," said Ed Shelleby, his spokesman. "This list is carefully protected, and Senator Franken's office always make sure not to rent out the names of those who ask that their name not be shared."