I am pretty convinced if 100% voting was compulsory and could be possible that republicans would never lose a presidential election ever.
I believe it would be the opposite.
The majority of America who are not registeted nor vote I would feel confident are isolated, more rural families who generally vote more republican.
"They’re younger. Roughly a third (34%) of nonvoters are younger than 30 and most (70%) are under 50; among likely voters, just 10% are younger than 30 and only 39% are under 50.
They’re more racially and ethnically diverse. Fully 43% of those who are not likely to cast ballots Tuesday are Hispanic, African American or other racial and ethnic minorities, roughly double the percentage among likely voters (22%)."
While that was from 2014, those things suggest it'd weigh the other direction
I don't think that study likely aligns with the conditions I am stating.
What are the conditions? ---
Seplito Nash, Smelling Like the Vault since 1996 Step FOUR! Get Paid!