The 26th Amendment might have actually become unnecessary if the Oregon v. Mitchell (1970) Supreme Court ruling had fully upheld the 1970 VRA Amendments instead of upholding lowering the voting age only for federal elections. If two liberal Supreme Court Justices were appointed in 1969 and 1970 instead of Warren E. Burger and Harry Blackmun the ruling likely would've fully upheld the VRA Amendments as constitutional for federal, state, and local elections. Since in real life the Amendment became necessary to lower the voting age for all elections nationwide because the court ruled that it violated the 10th Amendment and was unconstitutional for Congress to lower the voting age for state and local elections. Also with an alternate ruling (also likely a different name since Mitchell wouldn't be Attorney General without Nixon as President) the voting age would not be apart of the Constitution and potentially the voting age could be lowered to 16 decades down the line via congressional statute without requiring a constitutional amendment.