Not sure sure about that. While rural population covers about 97% of the nation, it only accounts for less than 20% of the population (roughly 60 million people).
Of those, you have to subtract ineligible voters (children, etc), plus their turnout numbers which are actually no different than those of non-rural voters.
(Census bureau numbers here:
https://www.census.gov/newsroom/pres.../cb16-210.html)
This can probably be calculated, but their incidence over a federal election is likely to be roughly 20% also. If you split their voting into 70%-30% between parties (IIRC, last presidential election was 66% GOP vs 34% Dem), that would be a 24 million vote advantage.
Now, 138 million people voted in the last presidential election, so the incidence of those 24 million votes would be roughly 17%. It's likely no slouch on highly compe ive states, but overall, I don't know I would really call it formidable.
Perhaps the biggest problem is that while the Rural population has kept relatively steady, Urban population continues to grow at a much rapid pace.