That caution worked out fantastic for Viso and Barrichello.
Now if the commentators would just shut up about his diabetes
It's unreliable too - 6 mechanical DNFs in the 9 races so far.
RHR's made zero driver errors and had high reliability, thats usually a pre-requisite for a championship challenge but he's also a lot faster than the several years he's spent in the upper midfield eking out the odd win. If he does take this year's title, he'll be the first American driver to do it since Sam Hornish Jr in 2006.
Putting on old tyres when everyone else was putting on new ones has done it for him I think.