Let's look at the margin of victory of US presidents since 1976. Here we find the vote count for the Democratic and Republican candidate each year, and calculate the percentage difference between the two.
For the 2020 election, let's add in results from the WSJ as of Nov 8 2020. At that time it showed 75.2M votes for Joe Biden and 70.8M votes cast for Donald Trump.
The resulting table shows the raw vote totals as well as the percentage difference (such that the democratic victory are positive in the
dem_perc_win column below). Note, this isn't percentage of total votes, but percentage between dems and repub candidates. Also note that raw values mean little because of population growth.
|1976||Carter, Jimmy||Ford, Gerald||40680446||38870893||4.45|
|1980||Carter, Jimmy||Reagan, Ronald||35480948||43642639||-23.00|
|1984||Mondale, Walter||Reagan, Ronald||37449813||54166829||-44.64|
|1988||Dukakis, Michael||Bush, George H.W.||41716679||48642640||-16.60|
|1992||Clinton, Bill||Bush, George H.W.||44856747||38798913||13.50|
|1996||Clinton, Bill||Dole, Robert||47295351||39003697||17.53|
|2000||Gore, Al||Bush, George W.||50830580||50311372||1.02|
|2004||Kerry, John||Bush, George W.||58894554||61872711||-5.06|
|2008||Obama, Barack||McCain, John||69338846||59613835||14.03|
|2012||Obama, Barack||Romney, Mitt||65752017||60670117||7.73|
|2016||Clinton, Hillary||Trump, Donald J.||65677168||62692411||4.54|
|2020||Joe Biden||Donald Trump||75215986||70812803||5.85|
Overall, it's amazing Ronald Reagan won the popular vote by ~45% in 1984. In terms of the current election, it appears that last Republican president to achieve a larger popular vote victory than Joe Biden was George HW Bush in 1988, 32 years ago.