CHICAGO (CBS) — A veteran political observer in Chicago said the Republican Party’s leadership is finally taking Donald Trump seriously, but time is running out if they want to stop him from claiming the GOP presidential nomination.

University of Illinois at Chicago political science professor and former Chicago alderman Dick Simpson said he cannot recall anything similar to Thursday’s denunciations of Trump by 2008 Republican presidential nominee John McCain, 2012 nominee Mitt Romney and Romney’s 2012 running mate, current U.S. House Speaker Paul Ryan.

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Romney called Trump “a phony, a fraud,” and said he’s “playing the American public for suckers.” McCain said he has “many concerns about Mr. Trump’s uninformed and indeed dangerous statements on national security issues.” Ryan has denounced Trump’s failure to quickly and unequivocally distance himself from white supremacists who support his campaign, saying “this party does not prey on people’s prejudices.”

“I don’t think of an example in the last 50 years that I’ve been watching politics where this has ever happened before where, uniformly, the previous nominees of the party are saying this candidate is just unacceptable,” Simpson said.

Simpson said he is inclined to agree with much of the criticism leveled Thursday. He said, while Trump might be able to find Qatar on a map because of his international business operations, his grasp of foreign policy does not appear to be good.

He is also put off by Trump’s statements relative to Russian President Vladimir Putin, saying while it’s good for a leader to be strong, Americans don’t want an autocrat in the Oval Office.

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In fact, Simpson said, he believes some of what has propelled the Trump campaign through the primary season could help guarantee a Democratic victory in November.

He said Trump has generally collected about 35 percent of the vote, and said that’s not enough to guarantee victory this fall.

“Most of Trump’s wins have been with 35 percent of the vote, and that’s just among Republicans. It takes 50 percent of all voters to win the presidency, and it is a difficult problem for Trump to win the presidency if he is the nominee,” Simpson said.

Simpson said he believes the March 15 primaries, including Illinois, could well decide the nominees of both parties.

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“The March 15th primary here in Illinois and in other key large states like Florida may be the last chance to defeat Trump; and show that the voters in fact, on reflection, don’t want him,” he said.