42-44 Clinton/
Bush42-49 Clinton/
Carson43-44 Clinton/
Fiorina45-43
Clinton/Trump
46-41
Biden/Bush
45-45 Biden/Carson
46-43
Biden/Fiorina
51-40
Biden/Trump
44-44 Sanders/Bush
39-49 Sanders/
Carson43-44 Sanders/
Fiorina47-42
Sanders/Trump
From September 17 - 21, Quinnipiac University surveyed 1,574 registered voters nationwide with a margin of error of +/- 2.5 percentage points. Live interviewers call land lines and cell phones. The survey includes 737 Republicans with a margin of error of +/- 3.6 percentage points and 587 Democrats with a margin of error of +/- 4 percentage points.
http://www.quinnipiac.edu/news-and-events/quinnipiac-university-poll/national/release-detail?ReleaseID=2283