WASHINGTON — At Mitt Romney’s 2012 presidential campaign headquarters in Boston, top aides ordered red hats emblazoned with “The Long Slog,’’ a wry acknowledgment of the bruising primary that seriously weakened the eventual nominee and contributed to his defeat.
Four years later, the 2016 candidates may need hats that say “Long Slog 2.’’
The Republican nominating contest will probably take place over a grueling, months-long grind next spring. The large field, uncertain state of the race, heavy influence of super PACs, and quirks of the calendar have triggered some concern that the eventual nominee again could emerge damaged. There is even speculation about the possibility, however remote, that the convention would begin July 18 without a clear nominee for the first time since 1976.
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It wasn’t supposed to be this way. After the 2012 campaign, top Republican officials devised rule changes for a shorter nomination contest in 2016 so the party could more quickly rally behind a candidate and focus on defeating the Democrat in the general election. They wanted fewer debates as a way to limit cringe-inducing gaffes. They arranged for the nominating convention earlier in the summer. By design, it was meant to restore a greater sense of order to the process. But the contest is shaping up to be anything but neat and tidy.
The primary features a complex system in which candidates will be competing in individual congressional districts throughout the nominating contest, seeking to amass 1,237 delegates as part of a war of attrition. The outcome of Super Tuesday, with all delegates being awarded proportionally in 12 states (including Massachusetts) on March 1, could be a super muddle.
“It’s truly a wide open ballgame,” said Saul Anuzis, a former RNC member from Michigan who helped reconfigure the rules and is now supporting Ted Cruz. “The establishment has not rallied behind a candidate, the money people have not rallied behind a candidate, and the grass roots have not rallied behind a candidate. It’s unlikely that we have a drawn-out convention. But if there’s ever been a possibility, this is one of them.”
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The first four states will be important, as usual, at thinning the herd of 14 candidates when they begin facing voters in February. But after Iowa, New Hampshire, South Carolina, and Nevada are done, there are no likely states that would allow someone to be declared a winner at least until March 15, when Florida will prove to be a key barometer. That is the first day when states can hold winner-take-all contests.

With enough states alloting delegates proportionally — some 54 percent of the delegates will be distributed this way, according to the RNC — candidates could have an incentive to stay in the race longer in the hopes of catching fire. And if the field remains crowded for a longer period, the contest could drag on, illustrating the limited control the party has over achieving a speedy resolution.
“There’s only so much that the national party can do from a rules perspective,” said Josh Putnam, a political science lecturer at the University of Georgia. “You can’t plan for how many candidates are going to run.
“I don’t think there were people at the RNC who said we’re going to have 14 or 15 candidate vying for this in December 2015,” he added. “But that’s where we are. And it’s an unknown factor.”
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Traditionally, Putnam said, it begins to become clear who the likely nominee is by the time 50 percent of delegates have been allocated, which this time would fall on March 8. The nomination is often clinched by the time 70 percent of the delegates have been allocated, which under the current calendar would fall on April 26.
The biggest question marks remain Donald Trump and, to a degree, Ben Carson. They have commanded improbably strong first- and second-place spots in polls for months.
Jeb Bush and Marco Rubio will probably continue their heated rivalry, while Chris Christie and John Kasich attempt to get into the mix with them. Increasingly, establishment Republicans are worried about Cruz, who has a path to go deep into the race as one of the most conservative candidates remaining, but who they fear would lose badly to Hillary Clinton.
“The guy a lot of people are concerned about is Cruz,” said Tom Rath, an influential New Hampshire Republican and top Kasich adviser. “You’re seeing a lane that’s pretty open. If he were to win Iowa, which is not impossible, there’s a real pathway for him.”
Top officials at the Republican National Committee have been explaining to reporters some of the intricacies of the nominating contest. They are acknowledging that the process could become very difficult to follow, handing out a 20-page packet with maps and spreadsheets detailing how each state decides its delegates.
The consensus among Republican heavyweights was that in 2012, Romney emerged from the nomination fight as a weakened candidate, going up against an incumbent president who had a head start on the general election.
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“After 2012 we tried to be thoughtful and see what went wrong — and if there are things the party can control, what should be better?” said Ron Kaufman, a top Romney adviser and an RNC member from Massachusetts.
This time around, several changes were made to try to influence the process. The nominating calendar was moved back, and with no challenges by other states to try to get into the action early, the four early states won’t vote until February, rather than early January in 2012. The convention was also scheduled for mid-July, about six weeks earlier than it was in 2012.
But although the calendar is compressed, the race could also be more competitive. March is a crucial month, when nearly 60 percent of the total delegates will be awarded. The month begins with Super Tuesday, when voters go to the polls in 12 states. But under party rules, those delegates will be awarded proportionally, making it difficult for any one candidate to sweep up the necessary delegates.
Perhaps the most important date is March 15, which is the first day that states can hold winner-take-all contests. Some of the most delegate-rich states will be voting that day, including Florida (99 delegates), Ohio (66), Illinois (69), and Missouri (52).
“Obama and Hillary went at it in 2008, and it worked out fine,” said Sean Spicer, chief strategist and communications director for the RNC, referring to the five months it took Obama to secure the nomination. “I fully expect to have a nominee by April. But if it drags out, it could be a positive thing.”
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He said the primary emphasis in changing the rules was to move the convention up.
“As long as our nominee has a head start,” he said, “that’s all that matters.”
Matt Viser can be reached at matt.viser@globe.com.