Bush critic and staunch opponent of the War in Iraq, Senator Russ Feingold of Wisconsin looks increasingly endangered for reelection.

Former Republican Gov. Tommy Thompson has not yet announced his intentions to challenge Feingold. However, in a hypothetical match-up Thompson would soundly defeat Feingold.

From Rasmussen:

Thompson holds a 48% to 43% edge over Feingold. Three percent (3%) prefer some other candidate, and five percent (5%) are undecided.

Thompson's lead was expanded slightly from the same poll conducted last month.

If Thompson fails to declare, Feingold may still face a stiff challenge from two largely unknown candidates. Continuing:

Feingold leads real estate entrepreneur Terrence Wall 47% to 39%.

Against another potential GOP opponent, businessman Dave Westlake, Feingold currently holds a 47% to 37% lead but again fails to receive 50% support.

Any incumbent who attracts less than 50% support at this point in a campaign is considered potentially vulnerable.