I don’t think this is something Obama is doing as an election strategy — I think he’s deeply concerned about the possibility of a Trump presidency. This is unprecedented, I think:
WASHINGTON — In his strongest denouncement of Donald J. Trump so far, President Obama on Tuesday said Mr. Trump was “unfit to serve as president” and urged the leaders of the Republican Party to withdraw their backing for his candidacy.
Mr. Obama said the Republican criticisms of Mr. Trump “ring hollow” if the party’s leaders continue to support his bid for the presidency this fall, particularly in light of Republican criticisms of Mr. Trump for his attacks on the Muslim parents of an American soldier, Humayun Khan, who died in Iraq.
“The question they have to ask themselves is: If you are repeatedly having to say in very strong terms that what he has said is unacceptable, why are you still endorsing him?” Mr. Obama said at a news conference at the White House.
Mr. Obama said that in addition to Mr. Trump’s comments about the Khan family, the Republican nominee had demonstrated that he was “woefully unprepared to do this job.” The president said Mr. Trump lacked knowledge about Europe, the Middle East and Asia.
“This isn’t a situation where you have an episodic gaffe. This is daily,” Mr. Obama added. “There has to be a point at which you say, this is not somebody I can support for president of the United States, even if he purports to be a member of my party. The fact that that has not yet happened makes some of these denunciations ring hollow.”