Critics of Trump's presidential library fundraising say "there are no rules"

President Trump's efforts to direct millions of dollars to his future presidential library has drawn fresh attention to a lack of visibility into the identities or potential interests of the donors who are funding it, a longstanding Washington concern facing past presidents from both parties.

Two prominent Senate Democrats say they are preparing to introduce a bill Wednesday that would regulate fundraising for presidential libraries, according to documents shared with CBS News.

"Donald Trump is using his presidential library as a tool for bribery while he is still in office," said Sen. Elizabeth Warren, of Massachusetts, who is introducing the legislation with Sen. Richard Blumenthal, of Connecticut.