Former Florida governor Jeb Bush outlines his energy policy during a visit to Rice Energy, an oil and gas company based in Canonsburg, Pa. (Gene J. Puskar/AP)

The Republican presidential contest is not, regardless of what it seems some days, all about Donald Trump. There’s another dynamic unfolding that has almost nothing to do with the businessman-politician currently atop the polls but that will have a major influence on who becomes the party’s nominee.

This other struggle involves the competition among former Florida governor Jeb Bush, Sen. Marco Rubio (Fla.) and Ohio Gov. John Kasich. History suggests that whoever emerges triumphant in this three-way rivalry will be in a strong position to claim the nomination, though admittedly the past has been a poor predictor of events so far in this campaign.

Ever since Trump surged to the top of the polls, the other candidates have been trying to assess both his staying power and the cost-benefit analysis of engaging him. Trump and Bush have clashed almost from the start, with growing intensity. More recently, as Rubio has risen, Trump has taken aim at him, and Rubio has responded in kind.

None of the other candidates has a clear strategy for taking down Trump. But they all think he will look like a different candidate — and in their assessments, a less formidable candidate — once the field narrows to three or four finalists after the voting begins. So they are beginning to focus on one another as much as they are worrying about him.

With the first contests still months away, none of the three yet looks like a front-runner. In the average of recent national polls, Rubio and Bush run fourth and fifth behind Trump, retired neurosurgeon Ben Carson and former Hewlett-Packard chief executive Carly Fiorina. Neither Bush nor Rubio breaks double digits. Kasich doesn’t even break 5 percent.

Marco Rubio speaks during a meet-and-greet event Friday in Iowa. (Jessica Reilly/AP)

National polls at this stage are less meaningful than state polls. In Iowa, where the first caucus will take place in early February, Trump and Carson lead, with Sen. Ted Cruz (Tex.) currently third. Bush and Rubio trail the first three, and Kasich is even deeper in the pack. In New Hampshire, Trump also has a big lead, but Kasich is jockeying with Fiorina for second, with Carson and Bush next and Rubio farther back.

In recent days, Bush, Rubio and Kasich have shown how much they’re worrying about one another. They’ve been sniping at each other and making other moves that underscore the significance of their competition.

Rubio has long emphasized that the party needs a fresh candidate, not one tied to the past, an implicit criticism of his fellow Floridian who is part of an American political dynasty. Bush, a two-term former governor, has belittled Rubio’s experience, or lack thereof. Kasich, a two-term governor and longtime House member, has claimed that his experience and record are unmatched by any of the other candidates.

Advisers to the three anticipate more attacks ahead. “The Bush campaign is feverishly doing their opposition research on Governor Kasich and Senator Rubio,” said John Weaver, Kasich’s chief strategist. “An empire like that is not going to go quietly into the night. We’re expecting pretty sharp elbows to be thrown. We’re going to handle it head on.”

Past Republican nomination contests often have devolved into competition between a candidate from the center-right or mainstream conservative wing of the party and a candidate from the hard right or populist conservative wing. Most times, the candidate from the mainstream conservative wing becomes the nominee.

This year, the race is more scrambled because of the added factor of the apparent desire by many Republicans for an outsider or non-politician. That has elevated Trump, Carson and Fiorina and has forced the others to adapt. Rubio has been stressing that, despite being in the Senate, he’s really not of Washington.

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Instead of establishment vs. tea party, one GOP strategist describes the race this time as a competition between those in the anger, or anti-Washington, lane, vs. those in the aspirational lane. Bush, Rubio and Kasich all fall more into the aspirational lane.

What will make the difference? Based on how the three candidates are running, it’s clear that they see the path ahead in slightly different ways, though each has handicaps he must overcome to win.

Bush has repeatedly pushed back at Trump by arguing that anger and insults cannot win the presidency. He seeks to be the aspirational candidate, conservative enough because of his record in Florida to be acceptable to a conservative party, while offering a positive and inclusive message that reaches beyond the GOP coalition.

But many Republicans see Bush as least able to appeal across the entire party — not much more able to appeal to the hard right than Cruz would be able to attract mainstream conservatives.

Lodged firmly in the establishment wing as the son and brother of former presidents, he faces resistance on the far right and among those yearning for an outsider. His hope is that he can change perceptions of himself, outlast his rivals with superior resources and persuade Republicans that he’s their best hope to win a general election.

Sally Bradshaw, Bush’s senior adviser, said the key remains what it has been from the start of the campaign: to portray Bush as a conservative reformer by stressing what he did in Florida. “People don’t know that yet,” she said. “When that message burns in, his numbers are going to change. That’s his path.”

Kasich is looking to the traditional model. He is the compassionate conservative of 2016 who hopes to strike first in New Hampshire and build from there. His advisers believe that, eventually, he can reach across the divide in the party to become the nominee.

But the party has not only moved right in the past decade, it also has developed a harder edge than when George W. Bush ran as a compassionate conservative in 2000. Kasich’s support for expanding Medicaid under the Affordable Care Act is just one example of a position that will not sit well with many conservatives.

Rubio’s team sees crosscutting appeal as vital, a race that will favor a candidate who can best unite a fractured party. The senator’s goal is to demonstrate skills as a communicator, to show depth on the issues, to turn his personal story into a positive message for the party, to make as few errors as possible and over time generate enthusiasm across the GOP coalition.

Rubio, too, has vulnerabilities. His past support for a path to citizenship for undocumented immigrants, from which he has backed away, remains an obstacle in his path. So too does his personal profile, that of a youthful first-term senator with limited experience trying to become president — a profile not unlike that of President Obama when he first ran eight years ago.

David Axelrod, who was Obama’s chief strategist in both campaigns, often has said that voters look for a replacement rather than a replica in picking a new president. The adviser to one of Rubio’s rivals put it this way: “When was the last time this country elected two presidents with similar attributes?” Rubio will be trying to dissuade his fellow Republicans that he isn’t another Obama.

There are wild cards in the calculations of all three camps. Maybe New Jersey Gov. Chris Christie, who occupies similar space, will catch fire in New Hampshire and elsewhere, although the resistance to him within the party is significant. Fiorina has demonstrated fearlessness that has jarred even Trump and can appeal across the party. Carson remains a candidate of unknown potential.

Last, there is the Trump factor and what his support represents. For now, he remains the dominant force in the GOP race. But the advisers to Bush, Rubio and Kasich see a turn in the campaign heading into the final months of the year, one that will heighten the competition among them with significant consequences for their party.