Primary matters: how Republicans will choose President Obama's opponent in November.

• Position: NATIONAL

President Obama has announced he's running for re-election, but who his Republican opponent will be is still a question. Now after months of debates and polls and speculation, the actual voting begins with the Iowa caucuses on January 3 and the New Hampshire primary on January 10. It's unclear at this point if any candidate will be able to wrap up the nomination quickly, or if the battle will continue into the spring, or even until the Republican convention in August.

How did this system come about?

In the 19th and early 20th centuries, elected officials and party "bosses" chose presidential candidates at their party's conventions. Progressives began promoting primaries in the late 1800s, saying party bosses were cutting backroom deals to select nominees. The first presidential primaries occurred in the early 1900s, but it wasn't until after World War II that they began to play a critical role in choosing candidates.

What are the primaries about?

A primary works very much like a general election. Voters head to polling places to cast secret ballots, with states voting independently.

Based on the results, the state parties allocate delegates for each candidate to the national convention, which formally picks the presidential nominee. At the Republican convention, the winner needs a majority of the approximately 2,400 delegates.

How are caucuses different?

Some states, like Iowa, have caucuses rather than primaries. In caucuses, party members meet at the district or precinct level--gathering at schools, churches, or even private homes--to discuss the candidates and the issues and then publicly declare who they're supporting. Iowa has 1,764 precincts, each hosting its own caucus.

What's the role of the conventions?

In most recent elections, one candidate has collected enough delegates in the primaries to all but guarantee the nomination. This has transformed the conventions into little more than three-day-long TV ads for the candidates since there hasn't been any suspense.

But a tight race among the Republican candidates could lead to a convention fight for the nomination, as has happened in the past.

Why are Iowa and New Hampshire so important?

In a word: tradition. Since 1952, the New Hampshire primary has been the first major test for presidential hopefuls. During the 1970s, the Iowa caucuses--held before the New Hampshire vote--began to gain importance.

Is this system fair?

In recent years, other states have tried to get some of the early...