"The Disclose act is another attack on free speech and must be stopped," states the TPN email, adding, "Two Senators who seem to be on the fence on this one are Olympia Snowe and Susan CollinsSusan CollinsGOP rep faces testy crowd at constituent meeting over ObamaCare DeVos vows to be advocate for 'great' public schools GOP senators introducing ObamaCare replacement Monday MORE of Maine. Call their offices and tell them to vote against this bill."
The message included the phone numbers for the senators' Washington and district offices.
The email adds: "The Disclose act puts restrictions on spending for political speech, but amazingly enough only for those who generally disagree with [Democrats]. Certain groups, Democratic constituencies, like unions, are exempt from the requirements of the Disclose act."
Supporters of the bill say unions would have to comply with the legislation.
The Disclose Act was created in reaction to the Supreme Court's decision in the Citizens United v. Federal Election Commission case, which ruled corporations are covered under the First Amendment. The ruing essentially removed campaign funding limits for these organizations.
The bill enhances campaign disclosure rules beginning in 2011 by requiring major backers of campaign ads to make their contributions known publicly.
A vote on the bill is expected later this afternoon.