Extremely cool site - I ended up watching just about all of the campaign advertisements. It's great that the museum put such a conveniently web-accessible record of these together.
1. Has fear really been an effective tool in campaigning?I think it's quite likely. Seeing the ads make you stop and think, and wonder, what the effects of these commercials were. To me, they come across extremely biased, presenting only one side of view; for the uninformed and undereducated voter, the campaigns were making maximum use of fear.
2. Has one candidate done a better job (historically) at provoking fear?I don't really know. To feel grounded in an answer, I think I'd want to see some sort of polling or historical data showing what people's opinions were to the commercial (before and after viewing), and if their position changed in reaction to what they saw. I really don't remember any of my reactions from seeing these ads when I was younger (I wasn't born until 1969). I think fear definitely played a part, however, in some candidates leveraging it more effectively than others. And it almost seems like an ad based in fear without accurately showing both sides of the story is really something more akin to disinformation.
As an aside, this thread reminds me about how political disinformation campaigns go way back, and have been with us since the very beginning. I remember being told in political science classes that in early elections in the United States, a common tactic was to have people falsely spread the rumor in rural parts of the country just weeks or days before the election that the candidate they favored had died. Apparently, since news traveled slowly and might take days or weeks to reach its destination, a coordinated effort such as this could convince a significant number of gullible people that they might as well not bother to vote on election day, because their candidate was dead. Later, when technology made news quickly and readily available, the tactic died out, but we see that the information age brought new ways to spread disinformation to the uniformed, and to scare them with imagery and soundbites designed to elicit our fears.
3. How are the current campaigns using fear in comparision to previous campaigns?I think it's more subtle this time around, unless anyone can point out a current campaign fear advertisement on par with some of the gems at the museum site. Which gives us a little perspective on how maybe things aren't so bad with this election?

I wonder if the Internet has anything to do with this; that although the campaigns could run fear-based attack ads, information both for and against the facts of the given ad attack in question circulate quickly.