Colorado Democratic U.S. Reps Diana DeGette and Jared Polis are leading supporters of a move to force natural-gas drilling companies to disclose the chemicals they use to blast gas out of the ground in an increasingly controversial process called "fracking." The two lawmakers were joined Thursday by 46 members of Congress in sending a letter to Interior Secretary Ken Salazar asking him to back a proposal in which the Interior Department would require disclosure of all materials used in fracking operations conducted on public lands. The DeGette and Polis bloc faces strong opposition in Congress and, turns out, their main opponents are pulling down large donations from oil and gas companies.