For 'establishment' candidates, time to make up ground

It's tough being part of "the establishment." But Marco Rubio and Jeb Bush hope to change that Wednesday night.

In a Republican nominating process that has been handily dominated by "outsiders" Donald Trump and, more recently, Ben Carson, the mainline candidates are under pressure to deliver in the Republican presidential debate, taking place at the University of Colorado in Boulder and hosted by CNBC.

Rubio performed well in the first two debates and showed an ability to lay out detailed policy answers on economic issues. But it hasn't been enough to vault the senator from Florida into the double-digit terrain held by rivals Trump and Carson.

"Rubio might have the toughest job tonight. This isn't time to show you have policy chops. It's time to show you can trade punches, and insofar as policy delivers a counterpunch, great," said Jason Stanford, a Democratic political consultant who has worked on more than 200 campaigns. "But the people who matter to him believe he's smart enough. They just don't see him as strong enough."

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Sen. Marco Rubio and former Governor Jeb Bush.

Trump, who has made personal attacks on the rest of the field a central part of his strategy, has singled out Rubio for ridicule. The New York real estate magnate has accused Rubio of being soft on immigration and last month characterized him an "all talk, no action" politician.

"To become the establishment candidate, Rubio has to become the anti-Trump, in effect, to prove to donors, delegates and activists that he's tough enough to stand up to a bully," Stanford said.

Republican Presidential Debate

Big and increasingly anxious political donors will be closely watching Rubio and Bush, hoping for a standout performance — particularly on economic issues.

Bush was thought of as a shoo-in for the nomination, largely because of the support he enjoyed from business interests, even before he announced his candidacy, but he's lagged in the polls.

Glenn Hubbard, an adviser to Jeb Bush and former chairman of the Council of Economic Advisers, said Wednesday that the CNBC debate will provide Bush a chance for "serious" conversation about economic growth. "We will not do that," he said, "with the kind of policies Donald Trump is suggesting."

That chance can't come soon enough. Bush announced on Friday that he will reshuffle his staff and cut spending, which many took as an early sign of his campaign's demise.

Some of the former Florida governor's larger donors spent the weekend trying to remain optimistic and rally financial support for Bush.

"Jeb can't play the long game," Stanford told CNBC. "He has to live to fight another day until he's lived through enough days and weeks that his campaign's crisis of confidence has passed."

Wednesday's debate comes at a key time in the nomination contest, with the Iowa caucus only a few months away, on Feb. 1.