March 11, 2008 - McCain 42.53% of Popular Vote
March 24, 2012 - Romney 39.12% of Popular Vote
March 21, 2016 - Trump 37.04% of Popular Vote
So, which is more 40 percent of a little pie, or 37 percent of a really big pie?
Completely asinine comparison. In 2008, only 8 candidates were in the race at Iowa, 4 withdrew by Feb 7th. In 2012, only 4 candidates were in the race. In 2016, 12 candidates were in the race at Iowa, 3 withdrew after Iowa, 2 after NH, 1 after SC, 1 after Super Tuesday, and 1 after ST 2. 4 are still in. Perhaps your math skills suck or you’re making an anti-Trump point, but percentages are usually lower the greater the denominator.