This year, the Nevada caucuses were held earlier than ever before, so candidates focused a lot more attention on the state.
In the Democratic caucuses, Hillary Clinton beat Barack Obama after a closely fought battle.
Mitt Romney won the Republican nomination race, after committing a lot more time and money to the state than the other Republican candidates.
Candidates spent a lot more money in Nevada than in previous years, although most Republican candidates paid more attention to South Carolina, which held its Republican primary on the same day.
The heavily-unionised service sector workers in Las Vegas form a major voting bloc in Nevada, and are a key part of the Democrats' constituency in the state.
One key union, the Culinary Workers' Union, endorsed Barack Obama, but Hillary Clinton had the support of the main teachers' union.
Rural voters in Nevada tend to favour the Republicans, while the state's growing Hispanic population are classic swing voters, who could tip the state either way.
Key local issues include a controversial plan to build a nuclear waste dump in the state, which many Nevadans are concerned about.