1988...Robertson finishes 2nd in Iowa. Outsider, yes, but didn’t lead in the national polls like Trump has. Dole puts up a challenge before Bush 41 takes over.
1992...Buchanan puts up a stronger challenge than expected vs. Bush 41.
1996..OK, maybe Steve Forbes is somewhat like Trump (never held office)...for that matter Buchanan hadn’t either. Bob Dole eventually takes over.
2000...Bush dominates with a mild challenge from McCain.
2007...Giuliani led in many polls
2008...Huckabee wins Iowa, Romney does well before McCain takes over.
2012...Santorum, Gingrich, Paul do well before Romney takes over.
A parallel event would look like Jeb! elbowing Trump out.
But this time, the front runner really does have momentum.