President Obama on Tuesday issued his strongest warning yet about the Republican candidates for president with a two-word message on why voters…

President Obama on Tuesday issued his strongest warning yet about the Republican candidates for president with a two-word message on why voters should choose solemnly: nuclear codes

Bluntly questioning front-runner Donald Trump’s temperament, Obama said, "Whoever is standing where I’m standing right now has the nuclear codes with them and can order 21-year-olds into a firefight."

A restive electorate ultimately will decline to elect Trump, he predicted."The American people are pretty sensible," Obama said. "And I think they’ll make a sensible choice in the end."

Though he referred specifically to Trump, Obama also took care to warn about all of the GOP candidates. "Not a single one of them" is talking about some of the world’s biggest problems, he said

The words represented Obama’s most energetic criticism of the Republicans running to replace him. For months, he has mostly kept a studied distance from the fray and resisted invitations to engage in political analysis

But GOP candidates are promising to dismantle Obama’s entire legacy if they win the Oval Office, and polls show Trump dramatically in the lead in South Carolina going into its Saturday primary. Such numbers are infusing his campaign with more momentum on the heels of his decisive win in New Hampshire last week

Asked about the president’s comments at a South Carolina forum, Trump responded with relative restraint, saying only that Obama had done a "lousy job as president" and that he would have defeated him in 2012 had he run." For him to say that is actually a great compliment," Trump argued of Obama’s criticism

After two days of meetings with 10 Southeast Asian leaders here at the presidential getaway estate of Sunny lands, Obama said he was also worried about what the campaign speeches and interviews were doing to American relations abroad

Foreign observers are troubled by some of the rhetoric, he said. In the past, Obama had singled out Trump’s pledge to ban Muslims from entering the country and deporting anyone not living in the country legally

In a conversation with reporters at the close of the summit, Obama said Trump wasn’t the only one he was worried about." This is not just Mr. Trump," Obama said. "There’s not a single candidate in the Republican primary that thinks we should do anything about climate change.... The rest of the world looks at that and says, ’How can that be?’"

"I have a lot of faith in the American people. And I think they recognize that being president is a serious job," he said. "It’s not hosting a talk show or a reality show. It’s not promotion. It’s not marketing. It’s hard. And a lot of people count on us getting it right."

Obama also downplayed the fight on the Democratic side between Hillary Clinton and Bernie Sanders, saying there was broad agreement in his party on principles but "a difference in tactics, trying to figure out how do you actually get things done."

Obama said he might eventually express his view in the race but that "for now I think it’s important for Democratic voters to express themselves and for the candidates to be run through the paces."