It's August. We'd be saying hello to President Dukakis and Dewey and Carter would have beaten Reagan, if the election were held in August. Of course, Trump or any major Presidential candidate could overcome a deficit in August.
I won't touch 1948 because I have no idea how accurate polling was overall. However, Carter was not polling over 45% at any point post-convention, nor was Reagan ever behind by 10-15 points (in fact Clinton leads where Carter was at that point by 10-15.)
As far as 1988, Clinton's scenario is actually closer to Bush's than Trump's, as far as good approval ratings for the incumbent party.
I'm having an increasingly difficult time seeing Trump recover from where he's at, but if he does and ends up winning, 2000 would be the closest comparison polling-wise.
There are a number of parallels between 2016 and 1948.
One of the biggest parallels is the disconnect between the GOP Presidential nominee and the GOP Congress (which had a majority at that time). Dewey was a moderate Republican who ran on a "me-too" GOP platform that reflected a combination of conservative and liberal positions, but the Congressional party was dominated by conservatives who did not like Dewey or his platform. Truman, seizing on this, used his acceptance speech at the Democratic National Convention to challenge the Republican Congress to enact their platform into law within 100 days. He did this knowing that they wouldn't, because the Congressional GOP wasn't in line with the Dewey platform. They went along with Dewey because he was popular not just as Governor of New York, but as a crime-busting prosecutor who had been mentioned as a successor to J. Edgar Hoover (who still had a stellar reputation) as FBI Director. And Truman was right; the GOP argued about their own platform and passed nothing. Truman's labeling of the 80th Congress as the "Do Nothing Congress" had special meaning here, especially in an age where Congress was expected to affirmatively take action.
The difference is that in 1948, even conservative Republicans were OK with their "front man", Dewey. They were hungry for a victory at the Presidential level, and it had been a long time since that had happened. That's not the case for today's GOP, which has controlled the House for all but 4 years since 1995, and the Senate for 13 of the last 22 years, and dominates Governorships and state legislatures. They're more of the "Establishment" than the 1948 GOP, yet they've experienced a hostile takeover of their Presidential nominating apparatus by a candidate who is opposed to the sort of trade and immigration policies that are the bread and butter of their well-heeled corporate contributors. I submit that THIS, and not Trump's temperament, comments, or Donald being Donald is the issue here. Trump's made it easy for these folks to balk, but they were going to balk anyway.
