A memo by McConnell's pollster, Jan R van Lohuizen, said the poll surveyed 815 likely voters in Kentucky from Oct. 16-19 and has a margin of error of plus or minus 3.5 percentage points.

"In these interviews we found that Senator McConnell led by a margin of 8%. Specifically we found that 49% of the voters intend to vote for Mitch McConnell, while 41% intend to vote for Alison Lundergan Grimes," van Lohuizen wrote. "Three percent of the voters plan to vote for David Patterson, while the remainder were undecided."

Grimes' top aide said the release of the poll was a sign that McConnell's campaign is "terrified."

"We knew the McConnell camp was scared, but the timing of this release — with public polls showing the wind at our back and undecideds breaking our way ... couldn't be more transparent," said Jonathan Hurst, Grimes' campaign manager. "Mitch McConnell can sense his 30 years in Washington are dangerously close to an end, and a two-paragraph memo from a pollster with a terrible track record only shows how terrified they've truly become."

MM Jan Poll Memo

This article has been updated to include the Grimes campaign's response.