Dumb question from a non-American

we narrow the field until the majority of states have had either a primary or a causus - All the candidates in the democratic party are selling themselves to all the democrat voters.  And vice versa all the republican candidates are selling themselves to the republicans voters. it's unusual for a democrat voter to be able to vote for a republican candidate - it's usually along party lines on how the field is narrowed down .  Then each party has a huge convention where the party officially announces who is running.  then it's a race between the 2 candidates with sometimes a 3rd person in the "independant party" running against each other. 

How's that for a simple explaination?

Not dumb at all. I don't know much about the NZ political process, either.

This is as good and short an explanation as I've seen (for primary elections):

http://usgovinfo.about.com/cs/politicalsystem/a/delegateprocess.htm

Hope that helps! I tried to explain/clarify, but as the process actually varies from state to state, the above link really is the best explanation.

Woah! So, really the Primary is like the heats, the conventions are the semi-final, and the election is the final?

Ours seems much easier, but then there are only 4 million of us, you could just phone everyone and ask them who they wanted!!

Thanks heaps for the explanations.  I hate feeling like a twit not understanding what's going on.

One other question then: I saw that voters have to register as belonging to Republicans or Democrats; can you change your preference? Are you required to register prior to elections each time or are you locked in from your initial registration at age 18 or 21 or whatever?

Thanks, Jac

Again, not a twit at all. It's not like we really understand it either . As far as registering, what you initially register as sticks, but you can change your party affiliation at any time, although there's usually some time limit before pending elections so that the change can actually be processed and you can vote as belonging to your new party.

Actually, you do not have to register as either Republican or Democrat. There are many other parties. You can also register as No Party Afilliation (NPA) which some people mistakenly label as Independent. That is understandable since the media often refers to independent voters. There is actually an Independent Party, which is not the same as NPA.

You can change your party affiliation anytime you want. States differ in their rules about whether NPA's may vote in the primaries or not. Florida does not allow it (my prior homestate) but other states do allow it.

You are required to be registered to vote before voting day. In NC, that means 60 days before election day. Not sure about other states.

Depends on the state. You can't vote in primaries in FL. You can in Montana, for example. A friend of mine in NC tells me that I can in NC. I need to register and find out!

Really???  Wow, I didn't know that.  In California you couldn't.  I'll have to check that out.

I didn't know that either! Not until I moved to NC and remarked to my friends that I couldn't vote in the primaries because I'm NPA. My Montana friend told me that was not the case for her, and my NC friend told me that she was pretty sure that wasn't the case in NC. I still need to verify but I have plenty of time - NC primaries aren't until MAY!

 Wiki has a good page on it.  Interesting...  There is closed, semi-open, and open.  I feel good about learning something new today!!!

http://en.wikipedia.org/wiki/Primary_election

I'm not registered for either party, but I can vote in the primaries in Virginia.   

To clarify, in Montana, we do not register party affiliation at all. We just show up on election day and decide whether we're in more of a Republican sort of mood or a Democrat sort of mood. No such thing as NPA here, or perhaps we're all NPA...

Congratulations!  Because of this post you now know more about the US election process then most Americans do

That's correct, Virginia has no "registered" voters of any party, anyone can vote in any primary...but only once   

Edit to add, the major parties in Virginia may or may not actually hold primaries. Sometimes a mass meeting is called rather than a primary