Updated at 5:15 p.m. ET
(CBS News) Republican business magnate Donald Trump on Tuesday maintained his skepticism of President Obama's place of birth and even suggested that presumptive Republican presidential nominee Mitt Romney would be unwise to write off the so-called "birthers" -- even as the Obama campaign is slamming Romney for failing to repudiate Trump's thoughts on the matter.
Trump, who joins Romney on the campaign trail today, tweeted, "@BarackObama is practically begging @MittRomney to disavow the place of birth movement, he is afraid of it and for good reason. He keeps using @SenJohnMcCain as an example, however, @SenJohnMcCain lost the election. Don't let it happen again."
The tweet came in response to aTuesday morning showing how the last Republican nominee, John McCain, debunked myths about the president. It asks why Romney won't, by comparison, disavow Trump's charges that Mr. Obama may not have been born in the U.S.
Asked Monday whether Trump's "birther" association gave him pause, Romney told reporters, "You know, I don't agree with all the people who support me and my guess is they don't all agree with everything I believe in. But I need to get 50.1 percent or more, and I'm appreciative to have the help of a lot of good people."
Romney hasn't given any further comment on the matter, but his staff has said Romney has no question about the president's origins. "Mitt Romney accepts that President Obama was born in the United States," Romney's senior adviser Eric Fehrnstrom said on CNN Friday.
On CNBC Tuesday morning, Trump maintained his skepticism. "Nothing's changed my mind...I walk down the street and people are screaming please don't give that up," he said. "I don't consider myself birther or not birther, but there are some major questions here."
The Obama campaign Tuesday afternoon released a statement slamming Romney for his "lack of moral leadership" on the issue.
"Mitt Romney's continued embrace of Donald Trump and refusal to condemn his disgraceful conspiracy theories demonstrates his complete lack of moral leadership," campaign manager Stephanie Cutter said. "Now he's even standing by silently as Trump assails John McCain's courage in standing up to the most extreme and hateful voices in the Republican Party -- all in order to raise money for himself. If Mitt Romney lacks the backbone to stand up to a charlatan like Donald Trump because he's so concerned about lining his campaign's pockets, what does that say about the kind of President he would be?"
Asked on CNN Tuesday afternoon whether he will try to convince Romney on birther issue, Trump said, "Not at all."