I think the worst ever would have to be McCain. At least Romney is not endorsing Obama like Mclame did.
No doubt about it.
McCain wanted only the GOP nomination -- his way of "sticking it to Bush". He didnt seem to want the presidency at all.
McCain also felt it necessary to insult his base at least once a day -- for some inexplicable reason.
Even Dole was superior to McCain. At least, Dole would've been a "signer" of GOP legislation. McCain, in the interest of "bi-partisanship", would've felt it necessary to sign Democrat legislation.
Who exactly do you think Willard helped elect in 2008 ?