People don't necessarily vote for a challenger to an incumbent unless they seriously question whether the incumbent deserves reelection. If enough people believe that Bush had good reasons to lie about Iraq, they won't necessarily see this is enough of a reason to look for someone else. And if they believe the lies about his tax cuts helping the economy (and remember, people have been conditioned to believe taxes are really, really evil so all tax cuts must be good), then they might decide the Bush was wrong on Iraq, but still deserves to be elected. Until enough people really start to see who George W Bush is and until they realize that they have been conned, the 2004 election is destined to be in the hat (and certainly the big money is eager to purchase another round of Bush policies).
Howard v Latham is a slightly different proposition, if only because there is much less of a gap between Howard's image and his actual record that there is between Bush's image and his record. The analysis is interesting because we know the Australian people also believe Howard lied over Iraq, but they do not yet see that necessarily a bad thing.
Certain passionate bloggers (yours truly among them) tend to think exposing the lie is enough. You actually need to expose not just the lying, but the motives for the lying and that is a much harder proposition.