Arizona Gov. Jan Brewer speaks to the media after a ceremony for the groundbreaking for the new Centennial Way to celebrate the upcoming Arizona centennial in 2012, Tuesday, May 17, 2011, in Phoenix. (AP Photo/Ross D. Franklin) (Ross D. Franklin/AP)

This Saturday is the deadline for Arizona Gov. Jan Brewer (R) to decide whether to move up her state’s primary to January. That decision represents what could be the first shoe to drop in another “front-loading” of the primary calendar that could include contests right after the New Year or even in December 2011.

But Arizona isn’t the only state threatening to crash the presidential party. In fact, there’s plenty of reason to believe some other states could advance their primaries as well.

To help you sort through it all, we’ve prepared a (semi) brief primer of what to watch as the states pick their primary dates.

What are the ground rules?

Four states have the permission of the national committees to hold their primaries and caucuses before March 6: Iowa, New Hampshire, South Carolina and Nevada. The Republican National Committee has said that any state that infringes on that quartet’s early status will forfeit half its delegates to the 2012 Republican National Convention in Tampa.

The default setup goes like this:

Feb. 6 – Iowa caucus

Feb. 14 – New Hampshire primary

Feb. 18 – Nevada caucus

Feb. 28 – South Carolina primary

March 6 – Super Tuesday (currently including contests in Colorado, Idaho, Massachusetts, Oklahoma, Tennessee, Texas, Vermont and Virginia)

After March 6, other states are free to hold their races at any time. But states with contests in March are required to allot their delegates proportionally, while states with races in April or later can award them all to the winner of their state — a system that (at least in theory) allows for the latter states to more sigificantly influence the nominating process.

When will the primary calendar take shape?

When Arizona makes a decision. Saturday, Sept. 3, is the first major deadline for a state that is pretty openly threatening to jump the calendar process.

“Arizona is the first domino to fall in this process,” said Josh Putnam, a Davidson College political science professor and the purveyor of the great Frontloading HQ blog. “If we get an answer this week, it’s going get the ball rolling.”

State law forces the governor to declare the primary date 150 days before it happens, and with Brewer threatening to move Arizona’s primary to Jan. 31, Saturday would be her last chance to name that primary date.

After that, the overall primary calendar could fall into place in about a month’s time. That’s because RNC rules require states to pick their primary dates by Oct. 1. Once those dates are set, then the first four states are allowed to move up accordingly.

What is Arizona likely to do?

It’s anybody’s guess. Brewer has repeatedly said she is leaning toward moving the state’s primary to Jan. 31, but her office has also suggested other ways to make the state more relevant in the presidential nominating process, including a debate.

“The governor has previously pointed toward Jan. 31 as a date that she is leaning toward, but nothing is set in stone at this point,” Brewer spokesman Matthew Benson said.

The argument for an earlier Arizona primary has both pros and cons. For one, the state’s current primary date is already in violation of RNC rules, so moving the date to Jan. 31 wouldn’t lead to any more sanctions than the state is already facing. Indeed, in order to avoid losing delegates, the state legislature would actually have to move the primary back to March 6 or later (Brewer can only move the date earlier, not later). So if the state legislature isn’t going to move the primary back in the next month, it follows that Brewer might as well pick Jan. 31 and move her state up in the process.

On the flip side, moving up Arizona risks the scorn of the RNC and may not even pay off in the long run. That’s because other states would likely move up as well – including the four designated early states – thereby diminishing Arizona’s importance. On the other hand, if other states are going to move up anyways, this is Arizona’s last chance to join them.

What other states might move up?

There are three other states that are considered significant threats to crash the party when it comes to the primary calendar: Florida, Georgia and Michigan.

Florida has a Jan. 31 primary, but in May, the state legislature passed a law creating a new committee to determine the Sunshine State’s primary date. Still, Florida Republicans have stated a desire to be the fifth state in the primary process, which would put them before March 6 and in violation of RNC rules. This is essentially the same thing Florida did four years ago.

Michigan also violated party rules four years ago, by holding a mid-January primary, and could do so again. Its primary is currently set for Feb. 28, and Michigan Republicans have voted to set the final date for between Feb. 28 and March 6. Feb. 28 is already an election day in the Wolverine State, so Michigan Republicans have to choose between convenience and violating RNC rules.

If either Arizona, Florida or Michigan goes on Feb. 28, of course, South Carolina could simply move its contest a few days earlier, and the four early states would still be the four earliest states.

Georgia law was recently changed to give the secretary of state the authority to change the primary date, and Secretary of State Brian Kemp can set it for anywhere between Jan. 31 and June 12. The most likely dates are March 6 or some time in April, but Kemp is guarding his prerogatives and hasn’t dismissed the idea of jumping ahead of March 6.

Are there any other states to watch?

A few other states are currently set for February dates, but aren’t likely to cause problems.

Minnesota’s caucuses are currently set for Feb. 7, the day after Iowa. But because delegates aren’t directly elected at the caucuses — a.k.a. a non-binding caucus — RNC rules don’t require Minnesota to go March 6 or after.

Missouri is also currently set for Feb. 7, but is expected to move its date to March 6. And New Jersey, while complicated, is expected to move from its current Feb. 7 to June. (Food for thought: if other states jump ahead, maybe these states just stick with Feb. 7.)

Things can change fast when it comes to setting primary and caucus dates, but states where it rests in the hands of one elected official — like New Hampshire, Georgia and Arizona — are generally the most flexible.

(For more information, we highly recommend the Frontloading HQ blog, which provides details of where each state stands in the process.)

What is the practical effect on the presidential race?

In short, it’s really hard to say. Some have wagered that Florida and Georgia advancing their primaries could help a Southern candidate like Rick Perry, while others think Arizona or Michigan would help Mitt Romney, given his ties to Michigan and the Mormon population in Arizona.

A more compact process with a big Super Tuesday certainly favors whoever can assemble the best national campaign and whoever has the most money, while a long, drawn-out process before Super Tuesday can allow a lower-tier candidate to build momentum with some strong early performances.

There are so many ways that the primary calendar could shake out, though — literally dozens and dozens of possibilities.

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