Menendez in the lead?

Last week we had a poll showing Republican, Tom Kean, Jr. with a small lead in his Senate race against Bob Menendez in New Jersey. Today a new poll is out showing Menendez with a nine point lead. Last month this poll showed Kean with a six point lead, so that's a fifteen point move in one month. Hard to know what to believe. This race is critically important if the Dems are going to take control of the Senate.