Same as now, back then you had a weak and ineffective incumbent who was a darling of the liberal establishment and with whom the mainstream media was heavily invested in.
So the media did all that they could that year to perpetuate the "dead heat" meme so that they could provide hope for the supporters of the incumbent and demoralize the supporters of the challenger (Reagan).
Fortunately it didn't work and it shouldn't work this time around either.
I never did buy the "Reagan surge" the last weekend of the campaign. I felt that Reagan was headed for a blowout victory all along and that the media - through their bogus polls - were artificially keeping the race close all the way to the end.
Yeah. I’m not popping the corks until o thug is gone.