Donald Trump and former Florida Gov. Jeb Bush are the two best known Republican presidential candidates, but several other candidates have higher net favorability numbers, according to Gallup's tracking poll.

Trump scored the highest familiarity rating at 92 percent, but his 20 percentage point net favorability rating trails ten of the 16 other major GOP candidates, according to the tracking poll that surveyed Republicans and Republican-leaning independents from July 8-21. More than 80 percent of those surveyed knew Bush, but his 27 percentage point net favorability rating trailed seven other candidates.

The candidates with the highest net favorability ratings, in order, were Florida Sen. Marco Rubio, a 42 percentage point net, retired neurosurgeon Ben Carson, a 40 percentage point net, and former Arkansas Gov. Mike Huckabee, a 37 percentage point net. But just 50 percent of respondents were familiar with Carson and 63 percent knew Rubio.

The only candidate with a negative net favorability rating in the tracking poll was former New York Gov. George Pataki, even though a greater percentage of voters knew Pataki than candidates such as Carly Fiorina and Ohio Gov. John Kasich.

As voters' familiarity with the large field of candidates rises, the higher net favorability ratings could have a larger impact on polling nationwide. Gallup's Andrew Dugan noted that the grouping of familiar candidates' instant name recognition poses a clear threat for those who are less known nationwide.