Illinois Senate Democratic candidate Alexander Giannoulias, hoping to hold the seat that was once occupied by President Barack Obama for his party, has been the target of more attacks funded by undisclosed donors than any other candidate–more than $4.4 million, according to a preliminary review of disclosures that explicitly state whether a candidate is supported or opposed by an outside group. Sen. Patty Murray, D-Wash., is second ($3.6 million) followed by embattled Senate Majority Leader Harry Reid, D-Nev., ($3.3 million) who is fighting a tough race for reelection against Tea Party favorite Sharron Angle.

Read a complete report on the phenomenon of dark money–political spending by organizations that don’t disclose their donors–at the Sunlight Foundation Reporting Group web site.

In addition to being one of its top targets, Reid has also had more dark money spent to support him–more than $596,000–than any other candidate.

The preliminary review shows that Rep. Bryan Lentz, D-Pa., who defeated ethically plagued Rep. Curt Weldon in 2006, has faced more dark money attacks than any other candidate–some $1 million. Second is Rep. Bill Delahunt, D-Mass., ($849,900) whose district Republican Scott Brown carried in the special election to replace the late Sen. Ted Kennedy and Rep. Bobby Bright, D-Ala., ($837,300) who has the distinction of having been attacked by both liberal and conservative groups. Republican Tim Burns has received the most support from groups that don’t disclose their donors–$312,200. Burns is seeking to unseat defense earmark king John Murtha’s successor and protege, Rep. Mark Critz, D-Pa.

The candidate analysis was based on spending by groups that have not disclosed donors to the FEC, and includes only independent expenditures. The full analysis looks at top races in the House and Senate and the big spenders of all forms of dark money in the 2010 mid-terms.

The Sunlight Foundation Reporting Group will continue to analyze outside spending patterns and report on our findings.