Another thing being ignored: The effect of Ted Kennedy's primary challenge, which probably explains much of Carter's troubles in the summertime. Kennedy did not give up until the day of his convention speech.
Take away the Ted Kennedy factor, and Reagan probably would have trailed the entire year until the debate.
The reason the Kennedy and Anderson campaigns existed at all was dissatisfaction with Carter. The patriotic support only goes so far, as both Bushes can attest. I lived through the election as a young adult and can attest that 'support' for Carter in any poll was either paper thin or given begrudgingly to avoid the right-wing. Yeah, it would have been possible without those two to poll well right up till people cast their vote, but the outcome would be the same.
This is not the case with Obama. He is liked and given due credit except by the extreme right. The idea of an Obama collapse from 'false' polling responses is a chimera.