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The poll showed Clinton with the backing of 48% of those between the age of 18 and 34 years of age - a vast improvement from the 31% support she had from the voting bloc in mid-September.
The big swing came as a result of dwindling support among millennials for Libertarian nominee Gary Johnson and Green Party nominee Jill Stein, as Trump actually boosted his millennial support from 26% in mid-September to 27% in Friday's poll.
Johnson's support among 18-to-34- year olds dipped from 29% in mid-September to 11% on Friday. Stein saw her numbers dip from 15% to 9% over that time frame.
Clinton's faced difficulties with millenial voters throughout the campagin, and has still not yet hit the level of support enjoyed by President Barack Obama in 2008 and 2012. She's enlisted Sen. Bernie Sanders of Vermont, her primary opponent who won over the support of a large swath of millenials, in addition to Sen. Elizabeth Warren of Massachusetts and, recently, former Vice President Al Gore to help woo younger voters.
The other major shift came among self-identified independent voters, who now favor Clinton over Trump 46% to 32%, with Johnson garnering 10% support. In mid-September, ahead of the first presidential debate, independents favored Trump over Clinton 42% to 35%, with Johnson getting 15% of the group.
Overall, Clinton led Trump 45% to 40% in a four-way race and 50% to 44% in a head-to-head matchup, a bump from her 1-point leads in September.
"Post-debate, Hillary Clinton checks all the boxes," said Tim Malloy, assistant director of the Quinnipiac University Poll. "With her base of women and nonwhite voters now solidly behind her and independent voters moving into her column, Donald Trump gets a wake-up call. The indies are leaving in droves."
That makes Sunday's second presidential debate seemingly a must-win for Trump. Clinton was widely viewed to have come out on top in the first event last week.
"Can Trump make a come-back in Sunday's debate or will Clinton score another W?" Malloy said.
Clinton now holds a 3.7-point advantage over Trump in the RealClearPolitics four-way polling average, and a 4.5-point edge in the head-to-head aggregate. On the day of the past presidential debate - last Monday - Clinton held 1.6- and 2.3-point advantages in those two averages, respectively.