The drop came as emails from her private server were released.
Support has been growing for liberal Bernie Sanders (I-Vermont), and even for a potential presidential bid by Vice President Joe Biden.
In the latest poll of Iowa Caucus-goers, Clinton claimed 37 percent of support, just a seven-point lead over Sanders with 30 percent. Biden has 14 percent, even though he has not announced he is in the race.
“I don’t know if her campaign is in trouble, but our campaign is doing great,” Sanders said this past weekend.
Meanwhile Monday, the State Department released roughly 7,000 pages of Clinton’s emails — including about 150 emails that have been censored because they contain information that is now deemed classified. Read more here.