Marco Rubio emerged from a razor-thin second-place finish in South Carolina's presidential primary on Sunday with the Republican field winnowed and his target clear: Donald Trump.
Rubio squeaked by rival and U.S. Senate colleague Ted Cruz in a vote on Saturday that cemented the appeal of firebrand outsider Trump as well as the failure of a candidate representing one of America's political dynasties, Jeb Bush.
The remaining Republican candidates are now scrambling for voters in 12 states that hold March 1 nominating contests on so-called Super Tuesday, the next milestone on the road to the Nov. 8 presidential election.
Rubio, a first-term senator from Florida who himself has come under attack for lacking governing experience, turned that criticism on Trump, a real estate mogul who has never held elective office.
Trump is long on rhetoric but short on specifics, Rubio said on CBS' "Face the Nation," challenging the front-runner who finished 10 points ahead in South Carolina to provide them.
"If you're running to be president of the United States you can't just tell people you're going to make America great again - I think you need to begin to explain exactly how you're going to do it, policy-wise," Rubio said on CBS, referring to the Trump campaign slogan "Make America Great Again!"
Rubio sharpened his criticism of Trump on healthcare policy and said he found his view of Russian leader Vladimir Putin troubling.
"I don't think he fundamentally understands exactly who Vladimir Putin is and or exactly what he's trying to do," Rubio said, quickly adding, "This is not an attack or anything of that nature."
In several television appearances, Rubio stressed his intention was not to "go after" Trump but to discuss issues.
Rubio has reason to be skittish. A hallmark of Trump's campaign has been consistent and highly personal savaging of his political rivals - or anyone else he perceived had attacked him, including Pope Francis. His most notable target was Bush, whom he began battering early on as a "low-energy" loser.
In television appearances on Sunday, Trump appeared uncharacteristically modest and took pains to lower expectations that he was a shoo-in for the Republican nomination.
He responded to Rubio's criticism on foreign policy without criticizing Rubio himself, saying on CBS he had "great knowledge" of the topic.
Cruz, who had expected his appeal to conservative and evangelical voters to give him an edge in South Carolina, said he was the only candidate who has beaten and could beat Trump.
On CNN's "State of the Union," Trump called both Rubio and Cruz talented men who could conceivably beat him for the nomination, along with the remaining Republican candidates, Ohio Governor John Kasich and retired neurosurgeon Ben Carson.
He then quipped, "You know, crazy things happen in the world of politics."
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