Let's say the US adopts a two-round system used only when no candidate reached 50%. A few elections must be 2-round. Who wins in...
2000- Bush/Gore
1996- Clinton/Dole
1992- Clinton/Bush
1968- Nixon/Humphrey
1948- Truman/Dewey
1916- Wilson/Hughes
1912- Wilson/Roosevelt
Also, 1860- a runoff between Lincoln and Breckenridge...
One man's opinion:
My version of 2-round voting assumes the only votes that change are all of the candidates 3rd and below, so more like IRV. It's also assuming arch-left go to the left candidate, arch-right go to the right candidate, etc.
2000-Gore 48.38%, G.W. Bush 47.87%, Nader 2.73%
Nader's 2.73% would put Gore over 50%. 51.5%-48.5% for Gore.
1996-Clinton 49.23%, Dole 40.72%, Perot 8.40%
Clinton would win off of 4th place Nader's 0.71% and would not even need to distribute Perot's 8.40%. 50.5%-40.9%-8.6% for Clinton.
1992-Clinton 43.01%, G.H.W. Bush 37.45%, Perot 18.91%
Perot had 18.91%, and assuming all the third parties distributed equitably, we're looking at something like 43.3-37.8, so Bush Sr. would have to take 2 out of every 3 Perot votes to win. I think Clinton would've still won this because that's too many votes advantage when so many people wanted change at the time. I'll say they split even. 52.5%-47.5% for Clinton.
1968-Nixon 43.42%, Humphrey 42.72%, G. Wallace 13.53%
Hard to determine definitively where Wallace voters would go. He was a Democrat, but the attitudes were shifting at the time, and the only Southern state Humphrey won was Texas. So I think it would be Nixon, but very close, like 51%-49%.
1948-Truman 49.55%, Dewey 45.07%, Thurmond 2.41%, H. Wallace 2.37%
Truman would win off Henry Wallace's 2.37% and Strom Thurmond's 2.41% would not even be needed to be redistributed. 52.2%-45.3%-2.5% for Truman.
1916-Wilson 49.24%, Hughes 46.12%, Benson 3.19%
Saying that the Prohibition candidate's 1.19% went to Hughes, Wilson would win by taking most the Socialist's 3.19% of the vote. 52.4%-47.6% for Wilson.
1912-Wilson 41.84%, T. Roosevelt 27.40%, Taft 23.17%, Debs 5.99%
Yikes. For starters, the Prohibition candidate's 1.38% would go to Taft. Unions at the time supported Wilson over Debs by and large, so say his 5.99% vote gets split with 2/3 of it going to Wilson and 1/3 of it going to Roosevelt maybe. So that puts us at: Wilson 45.9%, T. Roosevelt 29.5%, Taft 24.6%. Would the needed 1 out of every 6 Taft voters vote for Wilson to put him over 50%? I'd think so, but just barely, due to the bitterness of the election between Taft and Roosevelt. 51.0%-49.0% for Wilson.
1860-Lincoln 39.65%, Douglas 29.52%, Breckenridge 18.20%, Bell 12.62%
No clue. You had four completely different ideologies on display that were not very combinable. This would've been a very interesting election if it had gone to the House to say the least. You'd had anti-slavery (Lincoln), pro-slavery (Breckenridge), and ignore slavery (Bell) with Douglas getting the Henry Clay position.
