The way statistical sampling works, 1000 people in a population of 300,000,000 is actually good enough for most things. You can play around with numbers here to convince yourself, but at 95% confidence 1000 people will give an answer to within 3% of the true answer for the 300,000,000 population.
Probably the first time I’ve ever looked at a presidential lineup and simply hoped the two front-runners fall over dead as soon as possible.