How Negative Will Clinton Go in Iowa?

David Corn asks, and the answer from inside Clinton sources seems to be, as much as we have to.

An interesting flip of conventional wisdom from one:

"We once thought he had to win Iowa to stay alive," this Clintonite says. "We now think that we might have to win to stay alive." Will the fight get even more nasty as Iowa approaches? "There's still plenty of time for that," this person says. "And that's how things go in politics. There may be no choice."

From a politico's point of view, sure. But in the context of this race, doesn't going negative, especially by the book, feed right into Obama's narrative? Voters are always fed up, but this year seems worse than usual. Obama is telling them he's the one who can change that for good, that there is a choice in whether a candidate has to attack.

Of course, it depends on which attacks voters believe are unfair. It appears Iowans believe Obama and Edwards were on the right side of the line with theirs. Clinton's have sounded harsher, and she also faces a problem that plenty of voters think she's a bit nasty underneath anyway.

Little doubt she's tough as her campaign sells her. How much toughness will voters want?