SIOUX CITY, Iowa — New Jersey Gov. Chris Christie on Sunday lobbed barbs at Republican presidential front-runner Donald Trump during his final appeal to Siouxland voters, a day before Iowa's caucuses.

"It is almost impossible for me to believe that Iowans — Iowans — are going to give the state to Donald Trump," Christie said to 120 people at Morningside College during a 70-minute morning event.

Christie, mired in low single digits in most Republican polls in Iowa, also got in digs at two other GOP rivals who have emerged as Trump's chief challengers. He said Sens. Marco Rubio of Florida and Ted Cruz of Texas have the practice of talking about how they may change policies, while governors like himself do the nitty-gritty work of delivering for constituents. 

Christie also said Cruz and Rubio, in recent comments, have been parsing their records on immigration reform, since they are afraid of being labeled flip-floppers.

"What other Washington-speak will they use on you to make you think up is down?" Christie asked.

In his closing remarks, which many people said they enjoyed, Christie said Iowans should caucus for the candidate who will best serve to aid military members coming back from conflicts. He said that sober reality demands a president with the mature temperament to help people, so voters should not be acting on "an expression of anger."

"We are not electing an entertainer in chief, we are electing a commander in chief....This is serious business, everybody. Showtime is over, OK, showtime is over. Everybody loves a show, everybody loves a show. Showtime is over, it is game time," Christie said.

Three-fourths of the event was devoted to questions, as Christie responded to queries from people on climate change, immigration policy enforcement and campaign finance reform.

Suzan Stewart, of Sioux City, said Christie ably demonstrated his grasp of policy details.

"I enjoy every time I listen to him," Stewart said.

Stewart questioned him on a state policy detail, which led to her saying New Jersey has little sunshine to tap for solar energy.

Christie quickly responded with an apparent nod to his reputation as having a sometimes prickly side, gesturing to the crowd, "You are looking at New Jersey's sunshine, come on!"