Party leadership choices have consequences. Illinois largely missed the “Reagan Revolution” of the 1980’s, as well as the economic boom which continued into the Bill Clinton years. Neither Bush was competitive In Illinois.
While Springfield remained dominated by progressive Democrats, the party leadership wrote off Illinois as a hopeless “blue state”. It failed to grow the base of voters, which declined after the success of the Reagan years nationally.
Presidential year Republican voter turnout remains the same as in 1940 at just over 2.0 million despite population growth from 7.9 to 12.9 million.
Illinois Electoral College votes have declined from 29 to 20 because of the loss of 9 Congressional districts, reflecting the slow decline of Illinois relative to the rest of America. In the same years, Texas grew from 23 to 38. That means it grew from smaller than Illinois to nearly twice the economic size today.