Andretti and Peterson in the Lotus
Mario easily had the measure of Peterson in 1978. I know it's a popular perception nowadays that Peterson was somehow faster that season but it's simply not true. Just look at the Qualifying Positions;
Andretti Quali - 1, 3, 2, 4, 4, 1, 1, 1, 2, 2, 1, 2, 1, 1 - Avg Grid Spot =
1.86
Peterson Quali - 3, 1, 12, 6, 7, 7, 2, 4, 5, 1, 2, 1, 2, 5 - Avg Grid Spot =
4.07
Mario out-qualified Ronnie 11-3, taking 7 Poles to Peterson's 3
Andretti finished ahead in 6 of the 7 races they both finished, and looking at the Lap Charts there are only a handful of races where Peterson spent a significant amount of time in P2 behind Andretti. Here they are;
Belgium - P2 for Laps 40-56 and 67-70
Spain - P2 for Laps 53-75
France - P2 for Laps 10-54
Holland - P2 for Laps 1-75
I don't doubt that for a period of time in one of those races Peterson may have been a little quicker and was stuck in position behind the Lotus team leader, but to say that he was faster in 1978 is just erroneous.
I think that Peterson's tragic demise at Monza plays into this phenomenon. And also having one of those involved in the incident, James Hunt, shaping the perception of the 1978 Campaign factors in as well. Hunt rarely had anything positive to say about Andretti and on several occasions derided his title. We know how he ostracized Patrese about Italy 78 and I have no doubt that he harbored personal misgivings about his role in the accident. Helping perpetuate the myth that Peterson could/should have won the 1978 Championship was his way of making amends, I believe.