Would Romney have won without Amendment XXVI? Has it decided any election?

[RoboWop]

I'm sure this has been asked before, but the search function is not great. I can't think of another election that might have been flipped due to the 26th Amendment, which lowered the voting age to 18 from the previous 21.

1976 and 2000 are debatable, but almost impossible to say. 1992 is highly unlikely since Clinton won by such a significant margin, though it was the first time that Democrats dominated the under 30 vote.

The question is basically two parts:

1. What percentage of the under 21 vote did Obama (or Carter or Bush) win in each state?

Likely a large percentage in the case of Obama.

2. What percentage of the electorate was under 21 in the key states?

For 2012, these are namely Ohio, Florida, Virginia, and Colorado. I doubt Romney won the under 21 vote in any state he narrowly won (or any state except Utah).

For 1976 and 2000, the analysis is likely too complicated to be worth the effort. There were many close states won by each candidate in each election. We would need to be sure that no states which went to the loser would flip to the winner.

If we can determine that the youth vote did win Obama these states, I'd be interested to see just how many states Romney would win among 21+.

This paper (link to PDF, search for "Romney") says 2012, though results are inconclusive and the paper does not discuss in detail: https://academiccommons.columbia.edu/download/fedora_content/download/ac:161447/content/Wright_columbia_0054D_11340.pdf

My own research into the question of whether Gov. George Romney supported the amendment is inconclusive. But as the anti-war candidate in 1968, I can imagine he would have been sympathetic to the issue.

[RoboWop]

Here's CBS exit polling data on the youth vote in each election since the Amendment passed (except '72):

Youngest Cohort: Result (Percentage of Electorate)

1976 – 18-21: Ford 50-48 (6%)

1980 – 18-21: Carter 45-44-11 (6%)

1984 – 18-24: Reagan 61-39 (11%)

1988 – 18-29: Bush 53-47 (20%)

1992 – 18-29: Clinton 43-34-22 (17%)

1996 – 18-29: Clinton 53-34-10 (17%)

2000 – 18-24: Tie 47-47-6 (9%)

2004 – 18-29: Kerry 54-45 (17%)

2008 – 18-24: Obama 66-32 (10%)

2012 – 18-24: Obama 60-36 (11%)

2016 – 18-24: Clinton 56-35-9 (10%)

The only times Republicans have done better with the youngest voters are '76, '84, and '00 (and only barely in each case, which could be polling error).

[mvd10]

Looking at these numbers it's pretty safe to say that he wouldn't have won even without Amendment XXVI. Assuming 18-21 year olds voted similar to 18-24 year olds and assuming they were roughly 5% of the electorate (seems reasonable) the gap still would be 3.9-0.24*5=2.7 percentage points (or actually slightly more because numerator/denominator issues). It would be extremely unlikely that 18-21 year olds are distributed in a way that would allow Romney to win if their votes were removed.

This only would have been a thing if the election was extremely close (2000-like close) or if 18-21 year olds voted Democratic 90-10 while the rest of the nation voted 50-50 (in that case the result would go from 50-50 without 18-21 year olds to 50-48 with them assuming they're 5% of the electorate).

[SingingAnalyst]

I'm going to say the 26th Amendment has not decided any Presidential election.

2000 was so close in FL, that the "butterfly effect" (no pun intended) could easily have pushed it the other way. One poll I read showed Gore winning the youngest voters nationally 48-46.

So 2000 is a maybe.

While it is risky to assume that age gradients are consistent from state to state, it seems the 26th has contributed the following:

2004, flipped WI and possibly NH to Kerry.
2008, flipped NC and IN to Obama.
2012, flipped FL to Obama.
2016, flipped NH to Clinton.

I can't vouch for any state changes prior to 2004 (though NM in 2000 may have gone for Bush wihout the 18-20 y/o vote). Had Clinton won in 2016, her election would have been the first in which the 26th had an effect, as Trump surely would have won without it.