Are voters really so gullible/stupid?

Most of the political adverts I've seen for both the candidates are laughable in their content, either using blatently taken out of context quotes to try and twist their meaning, or missing out half the facts in something, or making really petty points to try and score points somehow. The thought I'm left with after seeing them is - are the voters really that stupid?

A few quick examples of some of the adverts:

http://www.youtube.com/watch?v=vRUQLYO6slM - somehow being able to find an area where you agree with your opponent makes you not ready to lead! Oh, and the implication that Obama is saying McCain is right all the time by decontectualising everything.

or http://www.youtube.com/watch?v=61O0SWlnNbw&feature=user - seeing as Obamas plans effectively mean tax cuts for all but the very wealthy (and tax hikes on the very wealthy), this again stinks of cherry picking your facts and ignoring other issues. Not to mention that it seems not only do you have to be completely clean, but every single person you've ever met in your entire life has to be palatable to the public or you'll be attacked for having them as an advisor or an associate.

Not that Obama's any better with some of his ads though:

http://www.youtube.com/watch?v=QJPo5IGTd0A - trying to pass off a tax cut for all companies as one specifically for oil companies is pretty pitiful (as is suggesting McCain is only doing this because he's received a bit of money from them). Then of course you have the notion of imposing a tax on companies to hand out money to lots of people - in reality if you do that those people won't be $1000 better off, and could even be worse off, due to the negative impacts of such a tax, although that's more of a poor policy point than blatant misinformation.

I would give another Obama ad to create more balance, but since there seem to be so many more negative McCain ads out there than Obama ones I'll probably just leave it (feel free to provide your own for either candidate though if you've got more examples of 'so-bad-they're-funny' ads!).

Fortunately none of them have quite reached these lengths, although sometimes they get close:

http://www.youtube.com/watch?v=68NEc8EvV2Q

Ultimately though, do these sort of adverts really work? I'm guessing they must (since why waste tons of money broadcasting them if they don't), but it's fairly disheartening to think that the people convinced by such adverts outweigh those put off by them. Why does it seem so hard for politicians to disagree about actual policy differences and the reasons for them taking a particular side without needing to try and throw mud at their opponent and twist everything they say? For example with taxation, you have McCain accusing Obama of raising taxes on the majority of people, and Obama accusing McCain of supporting huge cuts in taxes on oil companies - why can't they instead argue for/against increasing taxes on the rich+decreasing them on the poor, and keeping corp tax at it's current levels or decreasing it, and then let voters decide which policy they think would be best (via their choice of candidate)? There are valid arguments on both sides there, but they so rarely seem to be heard in this headline+spin-obsessed media age we seem to be in.