South Carolina set its Republican presidential primary for Jan. 21 on Monday, a move that is likely to push up the GOP nominating contest to start shortly after New Year’s Day — and possibly even before this year ends.

The move adds to what already was expected to be a more drawn-out battle, after the Republican National Committee passed a rule that will force states that hold earlier contests to award their delegates proportionally rather than winner-takes-all.

RNC officials made the change in hopes of lengthening the competition and keeping GOP candidates in the news, after a long Democratic primary monopolized the headlines during the 2008 primary.

Unless someone runs the table early and emerges as the overwhelming favorite, the race will drag out far longer than it did in 2008, when Sen. John McCain (Ariz.) essentially wrapped up the GOP nomination by early February.

“If the contest is competitive, then the delegate count becomes more important,” said John Ryder, a member of the Republican National Committee.

If the GOP race does develop into a delegate contest, it could take most of the first half of 2012. South Carolina and Florida are the first states to set their contests for January, and Iowa, New Hampshire and Nevada are expected to join them.

Three smaller caucuses will be held on or around Feb. 7, followed by two large states — Arizona and Michigan — holding primaries Feb. 28. In the intervening three weeks, no states are planning to hold contests.

All of those states except Iowa and the three holding February caucuses would lose half their delegates under RNC rules, reducing their impact if the race becomes a battle for delegates.

States will not be allowed to award all of their delegates to winners until April 1, meaning Super Tuesday on March 6 may not be nearly as determinative as it was four years ago.

The question for now is how early the early states will go.

South Carolina provided some clarity by setting its primary for 10 days before Florida’s primary on Jan. 31.

The Palmetto State became the first of the four states that the RNC has allowed to hold the earliest contests to move its vote from February to January.

“Today, South Carolina’s Republican primary restores order,” South Carolina GOP Chairman Chad Connelly said.

But whatever order Connelly was expecting was quickly thrown out the window.

Conflicting laws and rules in the other three early states are threatening to push the nominating contest into December.

New Hampshire state law says its primary must be held at least seven days before any similar contest, while the Nevada Republican Party’s rules say it must set its caucuses for four days after New Hampshire’s primary.

New Hampshire Secretary of State Bill Gardner, who has sole control over when his state’s primary will be held, confirmed Monday that Nevada qualified as a “similar contest” and that his state will go at least one week before its caucuses. That means one of the two states will have to give.

Those close to the process said a 2011 start to the nominating calendar remains unlikely, though not impossible.

“It’s unlikely, but I would not bet the ranch either,” said David Norcross, a former Republican National Committee member.

The Nevada GOP stuck by its party rules Monday, even as some suggested it could change them more easily than New Hampshire could change its law.

“Whatever Tuesday New Hampshire decides, we’ll be four days later,” said David Gallagher, executive director of the Nevada Republican Party.

New Hampshire’s primary has traditionally been held on a Tuesday, so if it takes place at least seven days before the next contest, that would put it on Jan. 3 or Jan. 10.

Iowa state law, meanwhile, says that its caucuses must be held at least eight days before the next contest. So if New Hampshire set its date for Jan.10, Iowa could go Jan. 2. If New Hampshire chooses Jan. 3, Iowa’s contest would have to be held in 2011 to comply with state law.

Despite that law, though, Iowa went just five days before New Hampshire in 2008. So these things have proven in the past to be malleable.

“They can do whatever they want, pretty much, as it is a state party decision,” Norcross said.

Indeed, the primary calendar is shaping up much like it did in 2008, with Florida going on the last Tuesday in January and South Carolina going 10 days before that.

The difference this year is, rather than Super Tuesday — in which many states hold their contests — being held in early February, it will be on March 6.