Since 1988, the Republicans have won the Presidential popular vote only once, in 2004. Popular opinion is that the recent Republican Electoral College advantage is somehow immutable. It is not. Indeed, 2024 could see Trump win the popular vote, and Biden the Presidency.
Simply: Trump has gained share in States which are either Democratic strongholds (New York and California) or in places where he already has the delegates (Florida and the Deep South).
By contrast, Trump and the Republicans have performed poorly in the battleground states won by Biden in 2020. In the midterm elections, marginal states like Arizona and Georgia should have been easy pickups for the Republicans, but instead they went backwards. The same happened in Pennsylvania, which was another State won by Trump in 2016.
The same trend played out in the House of Representatives. The Republicans handily won the Popular Vote beating out the Democrats by almost three percentage points. But they only just made it over the line in Congress, despite popular wisdom being that the maps favoured them. Why? Because the Republicans piled up massive wins in Florida, Alabama and the like, and gained lots of votes in California and New York, while losing delegates in Michigan and Pennsylvania.
Right now, no-one is offering odds on Biden winning the Presidency and losing the popular vote. They should. And bettors should not assume the Republicans will have the same Electoral College advantages in 2024 that they had in 2016.