SIOUX CITY, Iowa — Republican Donald Trump on Sunday rejected as “rigged” the FBI’s decision to close a renewed investigation into Democrat Hillary Clinton’s use of a private email server to handle sensitive information while secretary of state and vowed to continue pressing the issue that gave him a late rise in the polls.

“She’s protected by a rigged system,” Trump said of Clinton at a rally in Minnesota moments after the FBI announcement. “Hillary Clinton will be under investigation for a long, long time . . . likely concluding in a criminal trial.”

On Sunday FBI Director William Comey concluded the probe without revising its findings that closed the case in July.

“The rank-and-file agents at the FBI won’t let her get away with her terrible crimes,” Trump said later in Sterling Heights, Michigan. “You can’t review 600,000 new emails in a few days. . . . Now it’s up to the American people to deliver justice at the ballot box.”

Trump has ridden a late surge in the polls after Comey’s surprise announcement in October that it could reopen the email server case. But Comey’s announcement Sunday after reviewing newly uncovered emails may have dealt his campaign a blow.

Experts didn’t expect a huge swing in public sentiment because of the late announcement.

“Most minds are made up,” said Doug Muzzio, political scientist at Baruch College. “Those that aren’t, are not likely to see the FBI decision as determinative.”

advertisement | advertise on newsday

But Larry J. Sabato, director of the Center for Politics at the University of Virginia, said, “This is tremendous news for Clinton and is bound to give her a little added boost right at the end. She is on track to win anyway but this might lengthen her coattails a bit.”

In October, Trump had praised Comey’s October announcement that came 11 days before the election, saying the FBI had redeemed itself and he was certain the probe would be conducted properly.

“The announcement will not change much,” Susan Del Percio, a national political commentator who has worked on Republican campaigns in New York, said in an interview Sunday about the latest twist in the campaign. “All of that is already baked in the cake. . . . The polls are tightening and that is a sign that Republicans are coming home to Trump.”

“Comey was under heavy pressure from the Justice Department and possibly the White House to come out before Election Day with a finding,” said Richard Benedetto, a journalism professor at American University and former White House correspondent. “Whether it will make a difference at this late time is doubtful. . . . In this polarized atmosphere, few were waiting for the outcome of the email probe. Nonetheless, it can’t hurt Clinton.”

At his rally in Sioux City before the FBI announcement, Trump said the FBI “will be able to collect more than enough evidence to garner indictments against Hillary Clinton.”

He referred to his Democratic rival as “the prime suspect.”

“We could very well have a sitting president under criminal indictment and a criminal trial,” Trump said.

On Friday, Fox News Channel apologized for an inaccurate report earlier that Clinton would face indictment for her role with the family’s Clinton Foundation after an FBI investigation.

“It was a mistake, and for that, I’m sorry,” Fox anchor Brett Baier said Friday. Despite the Fox admission, Trump stirred up his Sioux City crowd Sunday with predictions Clinton still faces an impending legal crisis.

Trump and his supporters had grown optimistic about a late come-from-behind win based on the October FBI announcement.

advertisement | advertise on newsday

“I’ve been on the Trump train from the beginning,” said Rob Johnson, 20, one of a half-dozen University of Sioux Falls students who made the trip from South Dakota to the Iowa rally, leaving at 5:30 a.m. “But now the polls, because of the second email investigation so close to the election, are sliding in our direction, which is exciting.”

Although it was narrowing, Clinton maintained her lead in most polls released Sunday. The RealClearPolitics survey of national polls showed a range of results, from Trump up by 1 percentage point in the IDP/TIP poll to Clinton up by 5 points in the ABC News/Washington Post poll. The NBC News/Wall Street Journal poll had Clinton up by 4 points, while the McClatchy News/Marist College poll had Clinton up by 1 point. In Iowa, Trump had a 7-point lead in Sunday’s Des Moines Register/Mediacom Iowa Poll.

Trump has used the polls to try to transform from a tenacious underdog to emboldened front-runner, saying Clinton shouldn’t be allowed to run for president because of what he insists is her criminal conduct.

“In two days we are going to win the great state of Iowa and we are going to win the presidency of the United States,” Trump said in a shorter-than-usual 35-minute address, part of an 11th-hour cross country barnstorm.

“Our numbers are looking very good,” he said at the packed Sioux City Convention Center. “Tuesday is going to be a very good day.”

advertisement | advertise on newsday

Change like never before is only 48 hours away, Trump promised.

“In just two days,” he told the crowd, “you will get the change you have been waiting for your entire life.”

For Trump supporters, his rise in the polls was boosted further by a brief, but dramatic event in Reno, Nevada, Saturday night. A scuffle involving a protester in the crowd near Trump led Secret Service agents to shield the White House hopeful before escorting him offstage and behind a curtain.

Trump soon returned and finished his speech.

“Just nerves of steel,” said Ryan Benson, 20, another University of Sioux Falls student.

Trump continues to use Clinton’s now closed email case to ignite his fervent following as Clinton fights what political experts have called an enthusiasm gap.

But even before Sunday’s announcement, Trump still didn’t likely have the game-changer he needs, said Stanford University political scientist Morris P. Fiorina, who has written extensively about voter behavior and public opinion during the election cycle.

“Too many voters have made up their minds,” Fiorina said. “The worst possible outcome would be a disputed outcome” like the 2000 race between Republican George W. Bush and Democrat Al Gore. The results of that election remained in limbo for weeks until the United States Supreme Court ruled in Bush’s favor, making him the nation’s 43rd president and ending the dispute over Florida’s vote count.

Sixteen years later, with the Republican-controlled House and Senate refusing to approve President Barack Obama’s Supreme Court nominee, the high court could face a 4-4 deadlock in a disputed presidential contest.

The tight polls show it may happen this year.

“Look at the polling,” Muzzio, of Baruch College, added. “You could have five Floridas.”