What's so super about Super Tuesday?

ANALYSIS: On 1 March in the United States (Wednesday 2 March, in New Zealand), over a dozen states and territories will hold primary contests - for both Democrats and Republicans.

Here's a primer ahead of the action, starting with the overall process for choosing official party candidates for November's presidential election.

The super basics

• There can only be two. The two main US political parties are undergoing a tortuous process to choose who their official candidates will be for the general election in November. Yes, there will be news about this until November - it's the story that just keeps on giving.
• Each party holds a vote in each of the 50 states as well as numerous other territories (American Samoa, the Marianas etc). The state parties choose how and when to run their own contest, so each one is a little different.
• In each contest, candidates win delegates to vote for them at their party conventions in July - which is when the party candidates actually get chosen.
• It begins slowly with just four states in February: Iowa, New Hampshire, Nevada, South Carolina. They are a mix of small states where lesser-known hopefuls can make an impact. Then, once a few of the less likely contenders have run out of money or self-esteem, the whole contest picks up pace and goes national. That brings us to Super Tuesday.

What is Super Tuesday?

• Super Tuesday is the first day when multiple states and territories vote all at once: 13 for the Democrats, 14 for the Republicans. Most of the contests are held simultaneously for both parties.

Why is it "super"?

• Because there are a lot of delegates at stake. Tuesday begins a helter-skelter scramble to the finish, especially for the Republicans. By the Ides of March (15 March), Republicans will have allocated 60 percent of their winnable delegates and the Democratic party 40 percent. This is why the Republicans are panicking about Mr Trump's unexpected success - there isn't much time left to derail his campaign.
• Because the contests are in a wide variety of places, Tuesday will show much more clearly which candidates have national appeal and which appeal only to niche audiences.
• Because Super Tuesday might make it clear who might win and who should quietly tidy away their toys and look at other options, like former hopeful Chris Christie who decided this week to swallow his pride and ask (in code) to be Mr Trump's running mate.
• And because the media love naming things excitingly. It's a human trait, really, just consider the cool ratings we give volcanoes.

Key things to look for

• Can the Republican party regain a grip? Will a week's worth of last-ditch all-out attacks on Donald Trump by every Republican (other than Chris Christie) make him less popular or have the opposite effect? One super-PAC raised $20 million last week to make aggressive attacks on The Donald. If these don't work, the mainstream party will be all out of ideas other than changing the rules and hoping for a brokered convention.
• This is not how it was meant to be. The Republican party decided to front-load their selection process this year so there would be a clear winner well in advance of the convention and less blood on the walls. Instead, the race appears to have descended into an internecine blood-letting out of Dante. So much for Ronald Reagan's 11th commandment.
• Will Hillary Clinton make it impossible for Bernie Sanders? Some of Tuesday's states are Clinton home-runs (Alabama, Georgia, Tennessee) but others are more likely to back the Bern (Massachusetts, Minnesota). If he can't beat Ms Clinton in the northern states by as much as she beats him in the southern ones, he will not only be a lot further behind but will have no viable path to nomination unless there is a catastrophe for his opponent. She has the support of most of the super delegates (the third "super" thing in this article) so he needs to wallop her in the state contests - so far, he's not.