The Vietnam War
Vietnam war was opposed by higher and higher percentage of the American public the
longer it continued, with over 50% against by 1967 and about 70% by 1969.
in the 1968 presidential election, both Nixon(R) and Humphrey(D)
were pro-war. The only possibly-viable candidate
with a genuinely anti-war record, Eugene McCarthy, lost the
Democratic primary and abandoned the race.
Thanks to two-party domination, anti-war voters had nowhere to turn, and McCarthy
had no useful way to continue running.
With range voting, an anti-war candidate could have run with (in view of the polls)
a real chance to win, and without triggering "spoiler" voting pathologies.
Even without winning, genuine presure would have been
exerted on his opponents to address antiwar concerns.
Had the American public gotten to end the war in 1968,
1-2 million lives would have been saved. (Deaths after 1968 slightly exceeded deaths before 1968;
the war's total death toll was about 4 million, i.e. about 13% of Vietnam's population,
and there were a comparable number wounded.)