A number of federal lawmakers are coming under investigation as ethics complaints arise over possible connections between lawmakers and the university endowments that honor them.

Suspicions over nonprofit fundraising tactics used by corporations to influence Congress members have cast shadows on nearly a dozen current or former lawmakers, the New York Times reports. For example, an endowment at the University of Louisville set to honor Senator Mitch McConnell, was awarded a donation worth hundreds of thousands of dollars from a military contractor that later received a $12-million earmark sponsored by the senator.

Both the companies and lawmakers involved insist that the donations are merely for a good cause, yet groups such as Citizens for Responsibility and Ethics in Washington, allege that it is just another way to “curry favor,” Melanie Sloan, the group’s executive director, told the paper.

The increased scrutiny comes after Representative Charles Rangel, a New York Democrat and chairman of the House Ways and Means Committee, was accused by a House ethics panel of using Congressional letterhead to solicit donations from companies for a program honoring him at the City University of New York.

This week, the embattled representative took to the House floor to defend himself in a 31-minute speech, the Washington Post reports. In the speech, Rangel made it clear to his fellow lawmakers that he has no plans to resign his office.