Were there just 133 million registered voters in the United States for the November 2020 presidential election? No, that's not true: While we could not find a total for voters registered in for all 50 states as of November 4, 2020, we did find a cumulative number from before the election. The U.S. Census Bureau counted 153 million reported registered in 2018. With 21 states allowing citizens to registered at the polling sites on the same day they vote -- and North Dakota not even having voter registration -- that number is far short of the final 2020 tally. The number of eligible voters -- not the number of registered -- is a more relevant number. The claim of the lower number was used on social media to support a claim that if Donald Trump got 74 million votes, then Joe Biden could not have gotten 81 million.
The claim appeared in a post (archived here) shared on Facebook on December 19, 2020. It read:
If Everyone agrees that Trump got 74million plus votes and there are 133 million registered voters...how many votes were left for Biden????
This is what the post looked like on Facebook at the time of writing:
(Source: Facebook screenshot taken on Sun Dec 20 17:52:50 2020 UTC)
The 158,240,239 votes counted in the 2020 U.S. presidential election represent a 66.7% turnout of all eligible American voters, according to a calculation by the United States Elections Project. The estimate took into account the number of felons in the voting age population who were not eligible.
The project, which is based at the University of Florida, explained why pre-election voter registration numbers are not a good measure. Read this on its page titled "Why not calculate turnout rates as percentage of registered voters?" One major factor is that voters can register in many states on Election Day:
The way by which eligible persons can register to vote varies across states. North Dakota does not have voter registration. Other states have a policy known as "Election Day Registration" or EDR which allows individuals to register and vote on Election Day. In these states, voter registration as a turnout rate denominator is misleading since any eligible voter can cast a ballot if they so desire.
While we may not know the exact number of registered voters on election day, we know it was far more than 133 million in 2020.