That would be interesting having two peace candidates. First question, how do you negotiate and play poker when your position is known?
Perhaps the answer is, in more straightforward fashion. In point of fact, people do play and win poker tournaments even though other players know they are tight-aggressive or loose-aggressive or whatever.
In OTL, Johnson believed with considerable but not decisive evidence that Nixon had sabotaged potential peace talks in the Fall 1968. S. Vietnam's Thieu may have pulled out anyway, because in any coalition government he loses his position.
With differing candidates, you have much more of an unstable, shifting situation where people believe, well, if one side wins, we get a better deal.
With two similar candidates, not a guarantee that you'll get an acceptable peace treaty, maybe somewhat increases the odds.