The problem for the GOP is Trump is not going away anytime soon, said Robert Johnson, chairman of the RLJ Companies and longtime friend of the Clintons.
Trump commands 31 percent of support from likely Republican voters in New Hampshire, according to the most recent NBC News/Wall Street Journal/Marist poll, released Thursday. Cruz trails with 12 percent, followed by Rubio and Ohio Gov. John Kasich with 11 percent each and former Florida Gov. Bush with 8 percent.
"If [Trump] survives New Hampshire and rolls into South Carolina, he's right back where he is, and so the Republican establishment is now in this twin problem of trying to keep Cruz and Donald Trump out of the race," Johnson told "Squawk Box."
"I don't see how you have the bandwidth of trying to slay two dragons at the same time, and at the same time, pump up Marco and Jeb," he added. "You've got two guys that have to fall on their face almost simultaneously."
The question is whether outsiders Trump and Cruz can maintain their momentum, especially as Rubio surges, former Democratic Rep. Harold Ford Jr. told CNBC.
Rubio's message "is one that is American — pro-American, new American — and it looks like what the Republican Party wants to be going forward," said Ford, Morgan Stanley managing director.
Rubio finished with 23 percent of Iowa caucus-goers' support, well ahead of other establishment candidates such as Kasich, Bush, and New Jersey Gov. Chris Christie, all of whom attracted less than 3 percent.