Another House Republican is expected to step forward Wednesday in support of a new campaign finance bill, a House leadership aide has confirmed.

Although the GOP lawmaker remained unknown as of midday, the latest Republican backer will emerge before the legislation is formally introduced in the chamber Thursday.

When the still-elusive Republican emerges, the Member would join Rep. Mike Castle (R-Del.), who reached a deal on Monday with Democratic Congressional Campaign Committee Chairman Chris Van Hollen (Md.).

The now-bipartisan proposal is in response to a recent Supreme Court decision, Citizens United v. Federal Election Commission, which removed most federal restrictions on television ad buys by corporations, trade associations and nonprofit organizations.

Although few details of the bill are available, sources say that the main pillars are new stand-by-your-ad disclaimers for executives and new restrictions on ad buys by foreign companies, government contractors and Toxic Asset Relief Program recipients.