NEW YORK (CBSNewYork) — Media mogul Rupert Murdoch is calling for former Mayor Michael Bloomberg to enter the presidential race, but some political pundits aren’t so sure he’d have a chance.

In a pair of tweets Sunday night, Murdoch, the founder of News Corp., wrote that “With Trump becoming very serious candidate, it’s time for next billionaire candidate, Mike Bloomberg to step into ring. Greatest mayor.

“Agree much about Bloomberg, nannystate, etc, but still a great philanthropic executive who, with Guiliani, made NY the greatest,” Murdoch continued.

But Fred Siegel, senior fellow at the Manhattan Institute for Policy Research, said he thinks Bloomberg’s time has passed.

“If Bloomberg was going to run, he should have run in 2008 or 2012, when he was all geared up but didn’t,” Siegel told WCBS 880’s Rich Lamb.

“There is no opening for him,” he added. “What would Bloomberg run as? A Democrat? OK, if he wants to get into the race against Hillary (Rodham Clinton) and (Joe) Biden, yes. But I don’t think he wants that kind of bruising competition.”

Democratic political consultant Hank Sheinkopf, however, said the billionaire former mayor has the financial means to quickly join the race.

“Anybody can get into the race,” he said. “They have to be able to qualify in states throughout the country and, look, raising money is always a time-consuming effort. One thing about Mike Bloomberg, he doesn’t have to raise the money, and he can put an organization together almost instantly.”

Sheinkopf called Bloomberg a great manager and a “stabilizing force in a time of crisis.”

Bloomberg said in May 2014 that he has no designs on the White House.

“If I thought I could win, it would be something to consider, but you can’t win, and I’ve given 12 years to public service and I’m not going to be a candidate for president,” he said on CBS’ “Face the Nation.”

Bloomberg returned last year to running the financial media company he founded, Bloomberg LP.