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Former Democratic presidential candidate and DNC chairman Howard Dean is standing by his controversial tweet about Donald Trump's sniffles during Monday's presidential debate.

The Republican candidate sniffled repeatedly during Monday night's debate — setting off social-media memes and sparking the hashtag #TrumpSniffle.

After watching the Republican nominee spar with Hillary Clinton, the former six-term Vermont governor took to Twitter, suggesting that Trump's nasal troubles could be due to cocaine use.

Notice Trump sniffing all the time. Coke user? — Howard Dean (@GovHowardDean) September 27, 2016

In an interview with MSNBC's Kate Snow Tuesday, Dean acknowledged it's unlikely that 70-year-old Trump has a cocaine habit, but he didn't rule it out.

"It's something I think it'd be interesting to ask him and see if he ever had a problem with that," Dean said.

He added he wouldn't delete the tweet.

There was no immediate response from the Trump campaign to the question Dean posed. However, Trump told Fox News on Tuesday that there were "no sniffles" and that he didn't have a cold.