AHC: Two Rivals Battle It Out

The challenge here is to have the two (major party) nominees for President have versed each other in a previous election (for Governor, Senate, whatever). Give a little backstory to help us see what made it possible.
 
Okay, let's say the 1960 Presidential election goes differently. Maybe Nixon doesn't look as bad in the debate or Kennedy doesn't handle his religion as well. Kennedy still wins the popular vote, but the votes are distributed differently and Nixon manages to win the electoral college. Democrats are upset and feel robbed. So four years later they nominate Kennedy again. This time he wins, due largely to voter fatigue after 12 years of Republicans and the Civil Rights issues going worse. In 1968, Kennedy is running for re-election and Former Vice President Henry Cabot Lodge Jr. gets the Republican nomination. Kennedy unseated the incumbent Lodge in the 1952 Senate race, can Lodge return the favor 16 years later with a much larger title on the line?
 
I'm not saying it hasn't happened I'm curious for AH possibilities. One i thought of was have Romney challenge Kerry in 1996 after his close bid in 1994, lose by a few thousand votes. He comes back and runs for Governor in 2002. Kerry wins the WH in 2004 and Romney is the 2008 nominee against him.
 
Another possibility: Reagan decides to run for a third term as California governor in 1974, deciding he can still run for President in 1976 even in the middle of his term. He defeats Jerry Brown, but by a narrower margin than he had over Unruh four years earlier. Brown then wins the governorship in 1978 when Reagan leaves. Reagan goes on to be elected President just like OTL. Brown wins re-election in 1982 and in 1984, narrowly takes the Democratic nomination for President from Walter Mondale. Reagan curbstomps him the same way he did Mondale, only ITTL it looks even worse, because Jerry Brown will obviously not be winning his home state.
 
David Bonior decides that he can beat John Engler in a race for the Michigan Governor's mansion in 1998. He runs a tight race, but Engler wins 53% to 47%. Then, in 2000, Engler is tapped to be George Bush's running mate and they win. Engler resigns the Governor's seat and Lieutenant Governor Dick Posthumus serves the rest of his term. In 2002 Posthumus runs for a term in his own right, and Bonior runs again for the Democrats. This time he wins.

In 2007 Bonior declares that he will seek the Democratic nomination. He runs to the left of Clinton on economic issues ("I was never for NAFTA before I was against. I was just never for NAFTA."), but stays to her right on social issues like abortion. He wins the nomination. He faces off against Vice-President Engler (a sacrifical lamb for the Republicans) and this time manages to turn the tables on him, winning 53% to 47% nationally and taking their home state of Michigan.
 
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