After Donald Trump’s massive win in South Carolina, the Republican nominating contest turns, briefly, to the Nevada caucus on Tuesday. The contest has the feeling, though, of an opening act, killing time until the main act takes the stage.

A week later, on March 1st, 12 states will hold Republican primaries, mostly concentrated in the South. It has been dubbed the “SEC primary,” because seven of the states voting are in the South. The outcome will either confirm Trump’s status as the party’s presumptive nominee or serve as the prologue for a fight that strenches into early Spring.

There are 595 delegates at stake on Super Tuesday, around 25 percent of the total number of delegates. The biggest single prize on March 1st is Texas, which has 155 delegates at stake. The delegates at stake on Super Tuesday will be awarded proportionally, so even runners-up should win some delegates from each state.

The states voting on March 1st are: Alabama, Alaska, Arkansas, Georgia, Massachusetts, Minnesota, Oklahoma, Tennessee, Texas, Vermont and Virginia.

Colorado is holding a caucus on March 1st, but will not be voting in the Presidential contest. Last year, the state Republican party voted to scrap its Presidential contest, chiefly because the caucus vote had been dominated by anti-establishment candidates in recent elections. Republicans will still elect delegates to the Republican convention, but they will be officially untied to any candidate.

The territory American Samoa is also voting on March 1st. It too is skipping the Presidential contest and will simply elect nine unpledged delegates to the party convention in July.

In the last two Presidential elections, no candidate has swept all of the Super Tuesday contests. In the Democrat contest in 2008, Obama won 12 of the states making up that year’s Super Tuesday, while Clinton won 11 and an American territory. Obama just edged Clinton in the total number of delegates won.

On the Republican side in 2008, John McCain won nine states, Mitt Romney seven and Rick Santorum five. In 2012, Romney won six states, while Santorum won three, and Newt Gingrich won one state.

In both elections, for both parties, the candidate who did best on Super Tuesday ultimately went on to be the party’s nominee. Further back, Super Tuesday has also proved decisive. Bob Dole’s sweep of the contests in 1996 effectively confirmed him as the nominee. In 1992, Bill Clinton used his strong showing in the South on Super Tuesday to catapult him to the top of the nomination battle. He had lost both the Iowa caucus and New Hampshire primary that year.

Although Super Tuesday has always had a Southern flavor, the specific states voting on this pivotal day have changed throughout the elections. It represents the first “nationalization” of the primary contest.

Voting before Super Tuesday is confined to four early states that each have their own traditions and historic quirks. Each of these early states receives special attention from all the campaigns, providing an opportunity to build organizations and a campaign infrastructure. Financial resources are less important in these early contests, because campaigns can afford a great deal of retail politicking.

That dynamic changes heading into Super Tuesday, where candidates become stretched trying to criss-cross the country to hit all the states in a relatively tight window. Earned national media, expensive paid advertising and large national campaign organizations become the real currency of the campaign heading into Super Tuesday.

Polling so far has been sparse in the Super Tuesday states. Only a handful of polls have been conducted this month in any of the states. The most recent show Cruz leading in Texas (+7) and Arkansas (+4). Trump is leading polls in Georgia (+9), Virginia (+6), and Oklahoma (+5). A poll of Minnesota in late January showed Rubio leading in that state by two points.

No other public polling in Super Tuesday states has been released this year. Trump will likely begin most of the state contests with an edge, given his large victories in New Hampshire and South Carolina.

Trump is also the most likely to benefit from the “nationalization” of the primary that takes place on Super Tuesday. He has shown almost a preternatural ability to dominate earned media coverage throughout the campaign. His campaign, relying on large rallies and almost ubiquitous media attention, is particularly suited for the Super Tuesday contests.

Cruz has some advantages given the generally conservative make-up in voters in Super Tuesday states, his native son status in Texas, the richest prize on March 1st, and a large national political organization. Cruz also has a significant war chest that can be utilized for the expensive advertising necessary to compete in all the state contests.

Rubio will benefit from the likely consolidation of the mainstream Republican vote behind his candidacy in the wake of South Carolina. He doesn’t currently have the financial resources of either Cruz or Trump, but will be able to raise more money with Jeb Bush’s exit from the race. His spending to date, which has been second only to Bush’s, hasn’t been particularly effective, but it will keep him competitive.

Rubio may also benefit from a likely cascade of endorsements from other elected Republicans. While these endorsements aren’t necessarily beneficial with the overall electorate in these states, in a three-person race they could help him win some delegates. In South Carolina, it is clear from exit polls that Rubio was helped by the endorsements of almost the entire South Carolina Republican infrastructure.

That said, the Super Tuesday contests do present something of a problem for Rubio. It is hard to imagine him winning any of the states on March 1st. To date, Rubio has come in 3rd, 5th, and 2nd/3rd. No candidate, since Bill Clinton, has become a party’s nominee without winning one of the early contests. Clinton, however, was able to secure the nomination as a result of strong wins in Super Tuesday contests. That path is not open to Rubio.

Appearing Sunday on ABC’s This Week, Rubio said his campaign was looking to the contests beginning March 15th, when delegates are awarded on a winner-take-all basis.

“Well, when we get to the winner-take-all states we have to start winning,” Rubio said in response to a question about when he would win a primary contest. “Come march 15th, if you win a state, you get all of their delegates. We’ll be in real good shape for that.”

The March 15th contests are almost a month away. After the Super Tuesday contests, another eight states vote in primaries or caucuses before the winner-take-all contests begin.

Trump clearly has the edge going into Super Tuesday. Cruz should be able to compete in several of the states, however. At the very least, Cruz is favored to win Texas. Rubio, though, will generally be a spectator for these contests. “Beware the ides of March” is a good warning for the Rubio campaign. His candidacy will have to hope it makes it that far.