Candidates former Vice President Joe Biden and U.S. Senator Kamala Harris take the stage on the second night of the second 2020 Democratic U.S. presidential debate in Detroit, Michigan, July 31, 2019.

Through all of the 2020 Democratic presidential primary's early ups and downs, Joe Biden has consistently outpaced the field in polls.

The former vice president has led nearly every survey at both the national and early nominating state level. His support dipped following the first Democratic debate in late June, then stabilized in recent weeks.

Biden has so far shown staying power at the top of a jammed Democratic field even as his rivals' polling numbers wax and wane. Sen. Kamala Harris, D-Calif., has seen her standing change most dramatically: she surged from fourth to second in the RealClearPolitics national polling average after a strong first debate showing, then dropped back to fourth.