In a head-to-head match, Clinton leads by 12 points, 53-41, among likely voters.
The former Secretary of State maintains a 12-point lead, 50-38, when third-party candidates are included among likely and leaning voters, with Libertarian Gary Johnson following at 5 percent and Green Party candidate Jill Stein at 2 percent.
Clinton has expanded her lead since Monmouth University last polled at the national level in September, where she led by just three points, 49-46.
When third-party candidates were included in that poll, she led by four points, 46-42, with Johnson at 8 percent and Stein at 2 percent.
The Monmouth University poll was conducted via live telephone interviews on Oct. 14-16 among 726 likely voters, with a margin of error of plus or minus 3.6 percent.
TPM's PollTracker Average for the general election shows Clinton leading Trump, 47.8 to 41.7.