What's worse, as you said, it's that so many conservatives can't take a "yes" for an answer, or take credit for the good things that happened that they were responsible for, just because the consequences happen to be on somebody else's "watch". It also denies us credibility when we comment on truly bad things happening that are direct result of liberal programs (such as non-stimulus / Porkulus) because people start to tune out and reject the conclusions due to a priori false commentary.
"It ain't what you don't know that gets you in trouble, it's what you know for sure that just ain't so" - Mark Twain.
Negativity is the rule of the day. That's how they lost the initiative (and re-election) to Clinton who was able to take credit for all the good things happening at the time that he had nothing to do with.
Reagan owned faith in freedom and capitalism to always win through in the end. The present crowd isn't fit to clean his shoes...