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The optimum for any state for a Presidential nominee in a swing state is that the nominee can take advantage of the popularity (as defined as 'approval') by making shared appearances of the Governor. For a Democrat this might apply to Colorado and Virginia; for a Republican this might help in Ohio. Governors of Florida, Iowa, North Carolina, and Wisconsin will be of no such help to a Republican nominee.
Here are some approval polls on a national map of approval of incumbent governors. With caveat that this observation does not apply to non-swing states (thus Republicans are not going to win Connecticut, Maryland, Massachusetts, or Washington; Arizona is at best on the fringe of competitiveness for a Democrat and Kansas is a pipe dream), Republicans look to have some problems:
A positive approval rating under 45% is treated as a tie.
blue -- Republican incumbent with positive or neutral approval
20% -- tie (less than 1%) or positive approval under 45%
40% -- approval 45 - 49%
50% -- approval 50 - 54%
60% -- approval 55 - 59%
80% -- approval over 60%
green -- Republican incumbent with negative approval
20% -- approval 45 - 49%
40% -- approval 40 - 44%
50% -- approval 35 - 39%
80% -- approval under 35%
red --Democratic incumbent with positive or neutral approval
20% -- tie (less than 1%) or positive approval under 45%
40% -- approval 45 - 49%
50% -- approval 50 - 54%
60% -- approval 55 - 59%
80% -- approval over 60%
orange -- Democratic incumbent with negative approval
20% -- approval 45 - 49%
40% -- approval 40 - 44%
50% -- approval 35 - 39%
80% -- approval under 35%
No governor, governor in transition, or non-partisan governor -- white.
Positive approval under 45% -- (now treated as if a tie).
The newest poll takes precedence, but no internal polls or polls commissioned by a partisan entity, trade group, or union.
* -- appointed Governor.
