South Carolina Sen. Lindsey Graham ratcheted up his anti-Donald Trump rhetoric on Sunday, saying that the businessman 'polls like Lucifer' among women and Hispanics, and predicting 'another 9/11' if Trump implements his foreign policy ideas in the White House.

'There's a civil war going on in the Republican Party, obviously,' Graham said on the CBS 'Face the Nation' program, referring to the firestorm that erupted Thursday after former House Speaker John Boehner called Trump rival Ted Cruz 'Lucifer in the flesh.'

'John and I are very close friends,' Graham said of Boehner, 'but he's embracing Donald Trump, and I am not. Why? Because I believe Donald Trump's foreign policy is isolationism. It will lead to another 9/11.'

THROWING SHADE: South Carolina Sen. Lindsey Graham, at one time a long-shot presidential hopeful, bashed Donald Trump on Sunday by saying he 'polls like Lucifer' among women and Hispanics

TWEETER-IN-CHIEF: Trump castigated CBS News for ignoring the degree to which he trounced Graham in the Republican presidential primaries

Trump fired back on Twitter from Indiana after the interview aired.

'I watched Sen. Graham [on] @FaceTheNation. Why don't they say that I ran him out of the race like a little boy, and in the end he had no support?' the billionaire blasted.

Nobody remembers that he ran and he made a total fool of himself in the race!' Trump said Sunday during a rally in Terre Haute, Indiana.

Graham was a presidential candidate until a few days before Christmas when he dropped to less than 2 per cent in national polls.

On Sunday he latched on to the 'Lucifer' controversy and turned it back on Trump.

'There's been a lot of talk about Lucifer. I think Lucifer may be the only person Trump could beat in a general election,' the senator riffed.

'But when it comes women and Hispanics, Trump polls like Lucifer, so this [primary] is a contest between conservatism and Trumpism, and Trumpism will get creamed in the ballot box.'

He warned that Democratic front-runner Hillary Clinton could easily beat Trump in November's general election despite being a 'flawed' candidate.

'She will mop the floor with Donald Trump,' he said, 'because – with women and Hispanics, they hate Donald Trump because he's so harsh and he's so cruel ... in his policies toward illegal immigration, and he's so insulting toward women in general.'

GRILLED: 'Fox News Sunday' put Trump on the hot seat Sunday about his low poll numbers among women and minorities

Graham initially endorsed former Florida Gov. Jeb Bush, and later switched allegiances to back Cruz, a Texas senator.

'I'm advising Ted: "Go to the last vote",' he said. 'Trump's gotten 40 percent of the popular vote. That doesn't give you 1,237 delegates. I think you could still stop [him], even if you lose in Indiana.'

Trump shrugged off Graham's criticism on Sunday in Terre Haute.

'I don't want his endorsement or anything. Who cares?' he asked.

The billionaire added Sunday that he's finished calling Cruz and Ohio Gov. John Kasich the 'leftovers' in a primary contest he's been dominating for months.

Instead, he called them 'the two guys who are hanging by their fingernails.'