I would argue let’s use a few simple measures…

On the “personal economy” level… let’s look at the cost adjusted poverty rate, the unemployment rate, and the work force participation rate… these measures translate the economy down to regular people…

On the social level… let’s look at the national crime rate, inner city high school graduation rate, which party makes the most progress in the area of diversity as measured by the percentage change in the demographic composition of their party’s congressional members. The primary job of government is to keep its citizens safe, educate its people, and represent them. Let’s see how these measures change…

On the foreign affairs level… let’s look at whether the US enters any new wars or deploys more troops to existing ones… Trump did not participate in any new wars and drew down troops from overseas. On the nuclear front let’s see what progress N. Korea and Iran make in that area. On the trade front, let’s see what happens to our balance of trade.

Other economic indicators… let’s see what happens with inflation, the national debt, the percent of GDP spent by government.

These things are easily measurable.