Trump had erased an advantage in polls enjoyed by his Democratic rival, but the latest average posted by RealClear Politics now shows Clinton ahead by three percentage points, 43.8 to 40.9 per cent.
Libertarian candidate Gary Johnson nabbed 7.3 per cent.
Those nationwide poll results come as Clinton's numbers also improve in a number of critical swing states -- including the coveted battlegrounds of Florida, Nevada and New Hampshire -- following Monday's heated debate watched by some 84 million people.
Democrats are recruiting reinforcements -- especially in Florida, an infamous battleground state of more than 20 million residents and a consequentially high number of electoral votes. The deadline for voters to register in the Sunshine State is less than two weeks away.
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Both President Barack Obama and Vice President Joe Biden, who won the southeastern state in 2008 and 2012, will head there to try to sway voters next week.
Campaigning in Florida yesterday, Clinton described Trump as "unhinged," after the Republican presidential candidate fired off a pre-dawn tweet tirade against Machado.
In one tweet, Trump urged voters to check out a supposed "sex tape" of Machado, giving the White House race a surreal new twist.
The real estate mogul also caught flak after a soft-core Playboy porn film was unearthed in which he makes a cameo appearance.
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