The voter told President Trump: “Good evening Mr President. I have to say you have a great smile.” President Trump replied while a big smile and said “thank you very much”.
The voter added: “You’re so handsome when you smile.”
The interview host, Savannah Guthrie, described the voter Paulette Dale as leaning slightly towards Mr Trump’s election competitor Joe Biden.
Ms Dale voted for Hilary Clinton in 2016 but is registered as a Republican.
Mr Biden’s own town hall interview took place at the same time as Mr Trump’s on a rival TV channel.
President Trump’s interview was on NBC and Mr Biden’s on ABC.
Ms Dale’s comments towards Mr Trump send Twitter into meltdown.
One social media user wrote: “WHO IS THIS PERSON TELLING TRUMP YOU’RE SO HANDSOME??? What is happening???”
Another user said: “Might never stop projectile vomiting after seeing this woman flirt with Trump.”
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She asked Mr Trump if he expected to peruse his “previous efforts to cut the DACA program” if he is elected for a second term.
DACA or Deferred Action for Childhood Arrivals, is a program introduced by President Barack Obama in 2012.
The program is a measure to shield people from being deported who were taken to the US as children and did not have legal residency or citizenship.
Mr Trump’s administration have previously tried to end the program.
Mr Trump’s town hall interview was branded as a “disaster” by online viewers.
On Twitter user wrote: “This Trump town hall is a f***ing disaster for him.
“He just refused to denounce QAnon and now he’s having a meltdown.”
QAnon is a conspiracy theory that alleges the US President is battling a cabal of elite Satan-worshipping paedophiles.
The president refused to denounce the QAnon conspiracy theory during the interview.