SIOUX CITY, Ia. — Between questions about the federal deficit, immigration and climate change, Claire Campbell spotted her opening.

"It’s OK if you say no, but will you go to prom with me?" the 17-year-old high school senior asked Democratic presidential candidate Beto O'Rourke at a rally Thursday evening in Sioux City.

"As someone who did not go to prom because no one asked me, I’m really touched," O'Rourke responded. "This means more to me than you know."

"But somebody told me about your sign, so we came up with a counter-proposal," O'Rourke continued, lifting a white sign scrawled with blue marker.

"Will you caucus for me?" he asked Campbell as the crowd laughed.

After the event, Campbell said she was a little disappointed in O'Rourke's answer, "because, like, I need a prom date. But his counter offer was pretty good."

O'Rourke likely was disappointed in Campbell's response, too: She's from South Dakota and can't participate in the Iowa caucuses.

2020:Joe Biden leads Bernie Sanders, Beto O'Rourke, Kamala Harris in latest Quinnipiac poll

Fundraising:Democratic candidates boast fundraising totals as 2020 race heats up

Opinion:Where's the beef? Being Beto won't be enough to fuel an O'Rourke presidential campaign.

2020:Beto O'Rourke officially announces run for president