Senate Democrats are renewing their push for campaign finance legislation without the support of Republican Sen. John McCain, removing the bipartisan support needed to keep Republicans from blocking the bill.

The Senate will vote on Monday to advance the DISCLOSE Act, which would force outside spending groups that can spend unlimited sums to influence federal elections to disclose their donors. Although in May McCain told The Hill he was in discussions with Democratic Sen. Sheldon Whitehouse, the lead sponsor of the DISCLOSE 2012 legislation, and said he would support a bill that addressed the issue of union contributions as well as other outside contributions, the formerly outspoken campaign finance reform supporter did not sponsor the new bill.

McCain said he would not support the law until it is revised to cut out favorable treatment toward Democrat-leaning labor unions. However, Democrats claim the legislation -- which says Super PACs, corporations and unions alike must disclose the names of donors contributing more than $10,000 on independent political expenditures -- does not offer any breaks for unions.

The current bill is watered down version of the original DISCLOSE Act, which was introduced in response to the U.S. Supreme Court's 2010 Citizens United ruling. The first version would have restricted election spending by various groups, while the current draft focuses solely on disclosure.

Although McCain has been viewed as a staunch supporter of campaign finance reform, the Arizona Republican has strayed from that cause in recent years. Although the former Republican presidential candidate --who authored the Bipartisan Campaign Reform Act along with former Sen. Russ Feingold -- recently called the Citizens United decision allowing unlimited contributions from Super PACs a combination of arrogance, naiveté and stupidity the likes of which I have never seen, he has also indicated that any attempt to reform the campaign finance system would be shot down in the current Congress.