Kerry after all had the NAVY on his side - he was a genuine war hero. The protesting was an issue but Kerry was prominent enough to see that he was not a freaky long haired anti-war Maoist. Nixon feared him because he was as he was described in a book on Vietnam written in the 1980s as "the boy any parent would be proud to have as a son" and it mentioned that he was at the time the book was written Lt Gov of MA. One thing that makes it harder is that Obama is not being called for anything he did - but for things others did.
I know that you are using Jews as an example, but because I think the Jewish community is doing many things right - here is what I have seen. (I do think that this may have hurt Obama some in the primary, but Obama is lucky that at least in my synagogue there is little love for McCain. Many feminists (and we have lots) are very pro HRC and she is from the next state over - those factors rather than the smears are the basis for her doing better.)
The Jewish population was anti-war way before the rest of the country and most are very skeptical of quilt by association. I've posted a web site set up by Jewish Democrats against those smears several times. Now, I got it from my husband's uncle who was got the American Thinker smear as one of many people on an email list that was mostly war vets (WWII vintage), Republican and FL. He sent the smear thing to me to ask if I had stuff to counter it with (he knew I was for Obama and that I was active on the internet), but before I could pull together enough stuff, someone else on the list sent the anti-smear site via Reply ALL - and he sent it to me. (here's the link to the anti smear site:
http://njdc.typepad.com/stopthesmears/ ) In addition, I've been monitoring the weekly Jewish newspaper that I usually ignore and they have done a great job on this - hitting back at least 3 times this year - very prominently - second page - on attacks.
Your last paragraph is extremely interesting. What I can see is that I should look for local (or non-local for that matter) Jewish blogs and try to establish credibility as you did in VA. Because you are right that even with the things that are being done, it is obvious that we will be a target of a McCain effort. As you can see in my earlier post, I've been wondering how I can help in the general election. This is a community where I am involved in real life and can try to act as the next person at the water cooler after someone hears a smear. If enough people in a community know the truth, that could act as a vaccine that will keep that person from believing and then spreading the lies.
The real counter to McCain is to describe as Kerry, and now Obama, have that the Bush/PNAC policies have not made Israel safer - they have inflamed the entire middle east. That and pointing out McCain's other policies - which are not close to the values in the Jewish community and we are not really one issue voters. (Not to mention most American Jews are not big on Likud.)