FILE - This July 30, 2014, file photo shows U.S. Senate candidate and Kentucky Secretary of State Alison Lundergan Grimes, as she greets a group of supporters during a campaign stop at the Bullitt County Courthouse in Shepherdsville, Ky. After 30 years in the Senate, now seeking six more, Minority Leader Mitch McConnell of Ky., isn't terribly popular at home. Fortunately for him, President Barack Obama is politically toxic, a fact the Republican leader is banking on to help him to victory in the fall against Democratic challenger Alison Lundergan Grimes. (AP Photo/David Stephenson, File)

A SurveyUSA Bluegrass Poll, released Monday, gives Democrat Alison Lundergan Grimes the advantage over Republican Mitch McConnell in the Kentucky Senate race for the first time since May. Grimes, the Kentucky secretary of state, leads the Senate minority leader by 46 percent to 44 percent.

The new poll differs from the handful of other nonpartisan surveys released since September that give McConnell a lead ranging from 4 to 8 points, but it lines up with Grimes' internal polling conducted by Mark Mellman, a pollster with a history of correctly calling long-shot races for Democrats in North Dakota and Nevada.

HuffPost Pollster's Senate model continues to show McConnell as the favorite, with a 4-point edge over Grimes and about a 63 percent chance of winning -- moderately better than a tossup.

SurveyUSA shows the change coming mostly among Democrats, who now break 72 percent for Grimes and 21 percent for McConnell. In an August poll, SurveyUSA found 67 percent supporting Grimes and 25 percent backing McConnell.

National Democrats recently surprised some political analysts by ramping up their investment in the Kentucky race, spending $1.4 million on an ad campaign hammering McConnell for his long tenure in Washington.