Wakie, what do you mean by "With Eisenhower out of the running, you would have had a much stronger field"? Eisenhower was a can't-miss candidate for President, he was wooed by the Democrats and the Republicans as early as 1948.
I'm saying that because Ike was such a strong candidate there were few who wanted to run against him. If Ike declines to run then more Republicans (and probably more Democrats) run for Pres.
Sure, we can arrange a scenario wherein Nixon ends up as President. But odds are he wouldn't be as paranoid as he was in '68, nor would he be as experienced and skillful as he was in '68. Without Ike's political capitol Nixon could have very well been a terrible disaster.