Under fire for his health care vote and on the heels of a poll showing him trailing a potential rival by 31 points, Sen. Ben Nelson is taking out a television ad tonight to defend his vote.

The Lincoln Journal Star reports:

As a fresh poll measured the political cost of Sen. Ben Nelson’s health reform vote, he prepared Tuesday to take his case directly to Nebraskans during Wednesday night’s Holiday Bowl game.

Nelson will air a new TV ad in which he attempts to debunk opposition claims that the Senate legislation represents a government takeover, and he makes the case for health care reform.

“With all the distortions about health care reform, I want you to hear directly from me,” the Democratic senator says in the ad.

Nelson, dressed in an open-necked shirt and sweater, speaks directly into the camera during the 30-second ad.

The message will be launched during the Nebraska-Arizona football game and continue to air statewide for an undisclosed number of days.

Nelson doesn’t face reelection again until 2012. Needless to say, if an incumbent is forced to take out an ad almost three years before facing reelection, it typically isn’t a good sign.

And if his constituents aren’t happy with his vote on health care now, just wait until they have to sit through one of his ads during Nebraska’s bowl game.