The Daily Dot has the details on what you already suspected:
You may be getting trolled right now without even knowing it. Donald Trump supporters artificially manipulated the results of online polls to create a false narrative that the Republican nominee won the first presidential debate on Monday night. The efforts originated from users of the pro-Trump Reddit community r/The_Donald and 4chan message boards, which bombarded around 70 polls, including those launched by Time, Fortune, and CNBC.
These types of efforts aren’t always successful, but given the tight turn of online polls during debates, they’re highly susceptible to such pranks. In this latest incarnation, multiple Reddit users enlisted the Trump-supporting masses on r/The_Donald, which has over 200,000 subscribers, by posting dozens of online polls that are vulnerable to vote brigading, bots, and other forms of manipulation that make these non-scientific surveys notoriously unreliable.
The goal, according to comments surrounding the poll-manipulation threads, is to twist the mainstream media narrative that crowned Democratic nominee Hillary Clinton the victor. The effort spread to Twitter, where #TrumpWon became the number one trending topic in the United States Tuesday morning.
Hit the link for screencaps of messages that explain how to game the polls.
— Donald J. Trump (@realDonaldTrump) September 27, 2016