Update: From Larry Eichel of the Philadelphia Inquirer  

(Clinton's) 17-point loss in Wisconsin was a huge development, said Dante Scala, a political scientist from the University of New Hampshire.

Until Wisconsin, he said, Clinton had won primaries wherever her base of working-class women, seniors and Hispanics was inherently stronger than Obama's coalition of young people, blacks and upscale progressives.

"To use a tennis analogy, both candidates had been holding serve," Scala said during a talk at Villanova University last week. "Wisconsin was a breaking of serve." …

There's also the generational factor. "Maybe people don't want another baby boomer, another Clinton or Bush," said Doug Hansmann, a Clinton supporter from Madison, Wis. "The irony is that of the two Clintons and two Bushes, I think she's the best of the bunch."

Despite denials from the Clinton campaign and increasingly desperate shots aimed at Obama, Wisconsin voters can take pride that they dealt Hillary a near-fatal political blow last Tuesday.

From the Post:

One adviser, who spoke on the condition of anonymity to speak freely, said Obama's 17-point Wisconsin victory on Tuesday had started to sink in as a decisive blow, given that the state had been viewed weeks earlier as a level playing field.

"The mathematical reality at that point became impossible to ignore," the adviser said. "There's not a lot of denial left at this point."

Despite Clinton's public pronouncements of optimism, this adviser said: "She knows where things are going. It's pretty clear she has a big decision. But it's daunting. It's still hard to accept."

Analyses and comments after last Thursday’s debate:

Hillary Seems to Concede; Barack Obama Sizzles

Obama Texas Ground game will garner Wisconsin-like numbers

How Hillary Clinton blew a sure thing

Clinton Donors Worried by Campaign’s Spending