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MIAMI (CBSMiami/AP) – Coming off a fifth place finish in the New Hampshire primary, Senator Marco Rubio remains optimistic as he looks to South Carolina.

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“I want you to understand something. I want you to understand something. Our disappointment tonight is on me. It’s on me,” Rubio told a group of supporters Tuesday night. “I did not do well on Saturday night. So listen to this. That will never happen again.”

“There aren’t a lot of grownups who would get up in a room and say it’s on me, it was my fault. There were a lot of people who worked really hard for his campaign. He basically said look I had a bad debate. But it won’t happen again,” said Rubio supporter Liz Feren.

The senator from Florida came in behind lead vote getter Donald Trump, who was followed by Gov. John Kasich, Senator Ted Cruz and former Gov. Jeb Bush.

Appearing on NBC’s ‘Today Show’, Rubio maintained he’s “going to be the nominee. It is just going to take a little longer, but we are going to get there.”

After a third place showing in Iowa, things were looking up for his campaign until he was hammered by his rivals, especially New Jersey Gov. Chris Christie, in last week’s debate for being repetitive and scripted.

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Bush, who beat Rubio by less than a percentage point in the primary, told his supporters he’s looking forward to South Carolina.

“We need a President with a steady hand. With a proven record. Who has a servant’s heart. Who doesn’t believe it’s all about him. That’s why I’m running for the Presidency of the United States and why I’m so grateful to the people of New Hampshire. You’ve given me the chance to go to South Carolina we are going to do really well, thanks to you all.”

To give his struggling campaign a boost, Bush brought in a little family fire power. On Wednesday, his campaign unveiled a radio ad in South Carolina featuring Bush’s famous presidential brother, George W. Bush.

The former president says “There’s no doubt in my mind that Jeb Bush will be a great commander-in-chief for our military.”

The 60-second ad, “Steady Hand, will air throughout the state.

George W. Bush has also been enlisted to campaign for his brother in South Carolina, where Jeb Bush is making eight campaign stops in the state over the next three days.

One candidate who may be ready to throw in the towel is New Jersey Gov. Chris Christie who cancelled an event in South Carolina on the heels of his disappointing finish in the New Hampshire. Christie told a crowd of supporters in New Hampshire on Tuesday night that he was headed home to New Jersey to “take a deep breath” and assess what comes next.

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The man to beat remains Trump who garnered 35-percent of the vote in “The Granite State.” His juggernaut lead, however, will be tested in South Carolina, considered a hotbed of tea party groups and evangelical voters.