A head to head comparison of the Iowa 2020 General Election gives us an idea of the break down of the voters.      

President Donald Trump received 897,004 (54%) votes beating VP Joseph Biden who gained 758,211 (46%) by 138,793 votes in Iowa.

President Trump won 92 counties out of the 99 counties that make up Iowa. The record shows that VP Joe Biden won 7 counties.  

2020 IA Primary Election vs Presidential General Elections Counties Won              

Primary Elections

Presidential General Election

Primary Election

In the Primary, Trump won 99 counties in a 4 way match up. Sanders trailed behind him winning 4 counties with Klobuchar winning 1 county and VP Biden winning nothing in Iowa Primary.

2020 IA Presidential Primary vs Presidential General Elections w.r.t % Votes and Total Votes Won        

Presidential Primary Elections

Presidential Election

On a head to head count with the total votes between in VP Biden and President Trump between the Presidential Primary and General Elections, percentage (%) vote shift difference is 6% increase for President Trump and a 6% decrease for VP Biden. These percentages are represented by a vote increment of 865,581 for Trump and 724,179 for Biden at the Presidential General Elections.

Presidential Primary Elections

Presidential General Elections

During the 2020 General elections, a lot of total number of votes were cast. Aside the Electoral Votes, Popular Votes came to the fore as well. Further details regarding overall total votes cast, percentage contributed by the various states, and the winner of Popular votes will be updated soon.

Top 15 Counties in Presidential Primary Elections vs Presidential General Elections

All Candidates (Presidential Primary Elections)

All Candidates (Presidential General Elections)

Primary Elections vs General Elections

These 15 counties play an important role in these primary elections. If a candidate, can get a sizable majority in the larger counties (Polk, Linn and Scott), it becomes very difficult to win majorities in the smaller counties with out voter out reach and increased voter participation in them.

Top 15 Counties Comparison in Primary Elections vs General Elections

Presidential Primary Elections
VP Joseph Biden

Presidential Primary Elections
President Donald Trump

Presidential General Elections
VP Joseph Biden

Presidential General Elections
President Donald Trump

Polk, Linn and Scott, the three larger counties in Iowa voted in favor of Joseph Biden giving him a 60k vote advantage out of those counties. However, Trump's steady win at many more of the smaller counties was enough to overcome that deficit, making him gain an upper hand in the State of Iowa.

Related References: 2020 Iowa Primary Election Story, 2016 Iowa Primary Election Story, 2012 Iowa Primary Election Story