DES MOINES — President-elect Donald J. Trump said Thursday that the stabbing attack by a refugee last week at Ohio State University was a “tragic reminder” of the need to take a hard line on immigration, arguing that his administration would put the safety of Americans first in a way the Obama administration never has.

Mr. Trump, who visited the university’s campus on Thursday before speaking at a victory rally in Des Moines, said the attack — carried out by a Somali-born refugee who Mr. Trump has said should not have been in the country — had been “yet one more tragic reminder that immigration security is now national security.”

“No more games, folks, no more games,” he told several thousand people in a large event hall in downtown Des Moines, packed with supporters wearing bright-red caps emblazoned with Mr. Trump’s “Make America Great Again” mantra. “A Trump administration will always put the safety and security of the American people first. It’s going to be the American people first — it hasn’t been that way.”

In a 46-minute speech, Mr. Trump said his administration would crack down on visa abuses that harm American workers and reorder the nation’s immigration and trade policies to prioritize native-born people over foreigners, reprising some of the unalloyed nativism of his campaign.