A leading Democrat defended on Friday growing concessions to large interest groups in a campaign finance bill on which the House had been scheduled to vote Friday.

Rep. Chris Van Hollen (D-Md.), the assistant to Speaker Nancy Pelosi (D-Calif.), defended a series of exceptions Democrats allowed for the National Rifle Association and some other groups on disclosure rules under a new campaign finance bill, the Disclose Act.

Van Hollen said that while he would have preferred to include no carve-outs for groups, the organizations that are exempted from disclosure and transparency are large and well-known enough so as to not need so many rules.

"I would've preferred to get it done that way," Van Hollen said on ABC News's "Top Line" webcast, noting that his initial bill lacked the carve-outs. "But around here, the key thing is to get this bill passed. Because even with the changes, this will be a historic amount of disclosure."

The bill had to be pulled, though, after the exemptions — which also extend to the AARP, Sierra Club and some other groups — spurred a backlash among some centrist and liberal Democrats in the House, who threatened to vote down the law.

Pelosi pulled the bill from the floor despite it having initially been scheduled for a vote Friday.

Van Hollen said the bill, over which government watchdog groups have split, was most directed toward forcing transparency in quickly-formed groups with no clear source of backing, and that the groups exempted in the bill are far from unknown to voters.

"The groups we are really worried about are the groups that pop up overnight with shadowy names ... and don't have to disclose who their donors are," he said. "We are less worried about established groups with dues-paying members."