A candidate has the Electoral College advantage if their margin in the tipping point state is greater than their margin in the popular vote. So, for example, if the two major party candidates win 47% (R) and 51% (D) of the popular vote, but in the tipping-point state, they win 49% (R) and 50% (D) of the votes, then the Republican has an Electoral College advantage of 3%, since they lost the popular vote by 4% (i.e., their margin was -4%) but only lost the tipping point state by 1%.
The tipping point state is the state that gives a candidate the decisive 270th electoral vote, if you give the candidate their electoral votes starting from the state where their margin was largest and continuing in order. It is possible for there to be two tipping point states (this happened in 2020, see here for details), and in that case, the margins of the two will be averaged when determining the Electoral College advantage.
1,000
Demographic polling shows the R coalition shifting back towards the 2020 one, which had a massive electoral college advantage. I am pretty sure 2028 will not cause this market to resolve YES. Still not betting this below 50% though because of 2032, who knows what the coalitions will look like in that election
Historically, the advantage in the Electoral College alternates, with Democrats having the advantage in 2004, 2008, & 2012 and Republicans having the advantage in 2000, 2016, & 2020.
https://fivethirtyeight.com/features/even-though-biden-won-republicans-enjoyed-the-largest-electoral-college-edge-in-70-years-will-that-last/
I don't think that these are completely uncorrelated (or this market should be at 1 - (.5)^3 = 87.5%), but I think it is not unlikely for the advantage to reverse.