Real estate mogul Donald Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE is attacking two absent potential GOP rivals as he considers his own presidential bid.

The “Celebrity Apprentice” host warned Republicans at the conservative Iowa Freedom Summit not to vote for past Republican nominee Mitt Romney Willard (Mitt) Mitt RomneySenate Republicans face tough decision on replacing Ginsburg McConnell says Trump nominee to replace Ginsburg will get Senate vote GOP-led panel to hear from former official who said Burisma was not a factor in US policy MORE or former Florida Gov. Jeb Bush.

“It can’t be Mitt, because Mitt ran and failed (in 2012),” Trump said, arguing that Romney’s infamous comment about the 47 percent of people who feel entitled to the government’s support and the healthcare plan he pushed as the governor of Massachusetts will detract from his campaign.

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“I think beating Obama (in the last election) would have been much easier than the one coming up,” Trump jabbed Romney. “He choked. Something happened to him in the last month. He had that election won.”

Meanwhile, Trump also had harsh words for Bush, who is exploring a presidential bid of his own.

“You can’t have Bush. The last thing we need is another Bush,” Trump said of the son of President George H.W. Bush and the brother of President George W. Bush.

Trump accused Bush of being weak on immigration and border control, but more than anything he said Bush would remind voters too much of his brother, who left office with a low approval rating and made it difficult for Republicans to recover politically.

“When he runs, you have got to remember his brother gave us Obama,” Trump said. “Abraham Lincoln coming back from the dead couldn’t have won (in 2008).”

Trump went on to say he would be strong on immigration and work to repeal ObamaCare if he is elected president. The wealthy businessman has said he'll make a decision by May.

"I know what needs to be done to make America great again,” Trump said. “We can make this country great again, the potential is enormous, and I am seriously thinking of running for president, because I can do the job.”