Sen. Bob Casey Jr. (D-Pa.) has an 8-point lead over Republican Tom Smith, according to a new poll from Muhlenberg College and the Allentown Morning Call.

Casey leads Smith by 45 to 37 percent in the poll.

Smith has been spending millions of his own money on advertising while Casey's campaign has been relatively quiet, and some polls have indicated the race has tightened.

But there has been wide disparity between different polling numbers — some, including the last poll from this group, had Smith within a few points of Casey, while others have had the first-term senator with a comfortable double-digit lead.

National Republicans say they believe Smith has a shot at winning in the state, but have been less bullish about his prospects than those of other Republicans facing uphill Senate races in states like Maine. Democrats remain convinced Casey will be fine, and haven't spent any money to help him at this point.

The poll of 444 likely voters, a small sample size, was conducted from Oct. 17-21 and has a margin of error of plus or minus 5 percentage points.