Rep. Mark Kirk (R-Ill.) has taken the lead for the first time in a Public Policy (D) poll of the Illinois Senate race.

Kirk led state Treasurer Alexi Giannoulias (D) 37-33.

The last time Public Policy polled the race, before the February primary, Giannoulias led Kirk 42-34. Giannoulias had led Kirk in several other polls taken since the two became their party's nominees.

Since then, Giannoulias has come under fire for troubles at his family's bank, including a front-page Chicago Tribune story that revealed his family bank loaned $20 million to convicted felons, which Giannoulias denied being personal involved in.

Public Policy took the poll from April 1-5. The Chicago Tribune ran its story on April 2nd.

Even more bad news in the poll for Giannoulias: only 54 percent of Democrats support him while 77 percent of Republicans support Kirk. And there are a higher percentage of undecided Democrats -- 36 percent -- compared to 16 percent of undecided Republicans.

Public Policy's Tom Jensen writes in his analysis:

It's clear that the movement in Kirk's direction over the last two months has nothing to do with him and everything to do with Giannoulias. … The large mass of undecided Democrats are the critical bloc of voters in this race. If they come home to Giannoulias he'll probably still win -- this continues to be a very Democratic state. But if they- unhappy with both Giannoulias and [Gov.] Pat Quinn- decide to just stay home or even worse to vote Republican Kirk has a pretty decent shot at winning this. There may not be a state in the country where Democrats have a weaker top of the ticket at this point than Quinn and Giannoulas.