Under the slogan "Keep Iowa Great," President Donald Trump's two older sons invited themselves to the Midwestern state Monday just hours before the first test to see which Democrat would face their father in November elections.
"We're gonna beat them again," said Eric Trump.
Iowa caucus doors were due to open at 7:00 pm (0100 GMT Tuesday), with Vermont Senator Bernie Sanders in the lead as polls cast the 78-year-old standard-bearer for the party's left wing as the favorite.
He is followed by former vice president Joe Biden.
"When I see the mainstream ideals of socialism and communism actually being pushed -- I know we say this as a joke and everyone's laughing, but it's not a joke," warned Don Jr.
"While we've done a lot, there's still a lot left to be done, and Donald Trump's gonna do that," he added.
The rally, held just before voting for the Iowa caucus began, also featured President Trump's campaign manager Brad Parscale.
A group of Republican officials, including White House acting chief of staff Mick Mulvaney and commerce secretary Wilbur Ross, were also in attendance.
Parscale predicted that Sanders would do well in Iowa. And like Don Jr., Parscale mocked Joe Biden's performance in the polls after months of campaigning in the state.
"We're here in force to show the American people that this is a real movement. This president is serious about 2020," said Parscale.
The Republican caucus will also take place in Iowa Monday, but with significantly less suspense.
Although two candidates are running against Trump -- Joe Walsh and Bill Weld -- they are unlikely to beat the incumbent, who has the official support of the Republican Party and high popularity among his voter fan base.