I'm actually reticent to make additional specific criticisms of Hillary Clinton. Basically, she's had so much slime slung at her undeservedly, and I really don't need anything more than her (continuing) support for the war in Iraq to not support her. But I think her candidacy -- and more specifically, her husband's role in it -- makes a strong argument for basically forbidding the spouses of former Presidents from running for a party's nomination. Basically, President Clinton can't not come to Senator Cinton's defense, and can't not do so with all the ammo at his disposal. So you get disingenuous attacks on Barack Obama's opposition to the war, which will inevitably be recycled by the GOP if the Senator from Illinois wins the nomination: "Look, even Bill Clinton says you were lying about your opposition to the war..."
There's a long history of Dems using talking points in the primaries that get used against them later in the general. But it's a different thing entirely when a former President -- and the most successful politician from his party in a generation -- engages in these kinds of attacks.