This would be a disaster if he faced anyone other than trump.
In 1992 Clinton was absolutely walloping Bush Sr in the polls once the former wrapped up the Dem nomination. 1980 saw a much more varied polling landscape with Reagan pulling somewhat of an upset. However, he and clinton were popular challengers to unpopular incumbents. Trump is an unpopular challenger to an unpopular incumbent, so it's totally different calculus.
Reagan in the summer of 1980 was actually leading by 20+ points and many pundits thought democrats could lose up to 50 house seats . House democrats decided to basically give up on Carter during the campaign and probably saved quite a few seats while senate democrats did not and you ended up having a massive Republican wave in the senate .
