The Dismal Science

 Anthony Downs was an economist and political scientist who worked in a Washington D.C. tank.  He wrote the book: "An Economic Theory Of Democracy".  He died at age 90 on October 2, 2021. His book was written in 1957. 

Each voter would compare his expected utility of having party A (incumbent) in government (for another term, that is) with the expected utility of having party B (opposition) in government.  

The voter would vote in his own self interest based on his understanding of the issues as presented by the political parties.  Another option would be to not vote at all.  Not everybody does the research needed to make a good decision on their self interest and may opt out of voting.

I remember studying this issue in a course on presidential politics as an undergraduate at the University of Miami.  Its premise seems so obvious these days as to be trite.

Complicating this simple question is the local nature of politics in a very large and diverse country.  Individuals may also misinterpret the utility of various policies or even skip voting because the deck has already been stacked against them in various smaller political subdivisions.  

There is so much polling done, horse race analysis reporting, and sophisticated redistricting done that incumbency is over weighted and challengers are at a disadvantage except when the already low turnout is even lower in out year primaries.

As the understanding of this issue regarding voting has gained traction, even popular programs or projects can be sidetracked by an aggressive minority that may benefit from campaign contributions and corporations are considered like or as people in the law.  Sadly on a related front a retirement account or the stock market may trump values we have held dear.