Looks like Hillary Clinton has written off Wisconsin. Obama hit the airwaves earlier and harder, and Clinton's internal polling presumably shows she's going to lose, so she's cutting her losses in order to put her somewhat limited resources into Texas and Ohio. She'll almost certainly win Ohio, but if she can't win Texas as well then it's probably the end of the road...
Wisconsin's delegates don't matter to Clinton nearly as much as the PR value of a win here. She desperately needs to slow Obama's momentum, and a win, no matter how slight the margin, would do that. All that counts is the media narrative on Wednesday morning, so from Clinton's point of view Wisconsin is either a victory or nothing.
Most polls show Obama with a modest lead, in Wisconsin, although the most recent poll from American Research Group has Clinton up by 6%. The ARG WI polls have tended to favor Clinton compared to other polls, so you do have to take them with a grain of salt. Kind of interesting that in Texas the ARG polls tilt the other way.
Full disclosure: With Edwards gone I'm now supporting Obama for two main reasons. The first is that Clinton is just too blatantly corporatist for me. She was chair of the DLC and sat on the Wal-Mart board. Not my cup of tea. Second is that I want American politics to change, and the first step towards change is always bringing new people into the process and convincing them that they can make a difference. Obama, like Howard Dean in '04, seems to have that gift, and Hillary Clinton just doesn't. Irrespective of their policy positions, and they're not really much different in my opinion, I think that in the long run Obama is far more likely to push our country in the right direction, strengthen the Democratic Party, and build a healthier progressive movement.