Data & Demographics 1: Representative Samples, Increasing Independence, National Division · 9:50am Nov 3rd, 2018
Properly weighted surveys & polls accurately represent public opinion in the United States with participants ranging from 1,000 to 10,000 in number, generally; there exist exceptions (such as Pew Research Center's occasional 30,000-participant surveys), but a minimum of 1,000 participants exists as an industry-standard.
"How can a survey of 1,000 people tell you what the whole U.S. thinks?" from Pew Research Center.
"Methods 101: Random Sampling" from Pew Research Center:
"Sampling" from Pew Research Center.
"How Does the Gallup World Poll Work?" from Gallup.
"How can a poll of only 1,004 Americans represent 260 million people with only a 3 percent margin of error?" from Scientific American.
"Americans' Identification as Independents Back Up in 2017" from Gallup:
"Poll: Majority Blames both Trump & Media for Dividing Country" from Politico: