Nikki Haley, the last remaining rival to frontrunner Donald Trump for the Republican presidential nomination, is set to win Nevada's primary on Tuesday, but it will be a hollow victory as Mr Trump will secure all of the state's delegates in a separate contest on Thursday.
US president Joe Biden is expected to easily win Tuesday's Democratic primary after dominating his party's first nominating contest, in South Carolina, on Saturday.
For Republican voters in Nevada, Tuesday's state-run Republican ballot only has former UN ambassador Haley as a major candidate. She is therefore all but guaranteed to win, but it's largely meaningless.
That's because only candidates participating in a separate Republican caucus on Thursday can compete for the state's 26 delegates to the Republican National Convention in July when the party formally nominates its candidate.
The rival caucus is being run by the Trump-friendly state party, and only Mr Trump is on that ballot, almost certainly guaranteeing him victory on Thursday and all the state's delegates.
Voters can participate in both the Republican primary on Tuesday and the Republican caucus on Thursday.
In Tuesday's Republican primary, there is a "none of the above" option. Joe Lombardo, the state's Republican governor and a Trump supporter, has said he will vote "none of the above" on Tuesday and caucus for Mr Trump on Thursday, meaning Ms Haley's main "challenger" on Tuesday will likely be Trump supporters marking "none of the above" on their primary ballots.
The competing Republican ballots are the result of a conflict between the state Republican Party - run by Trump allies - and a 2021 state law that mandates a primary must be held.
Presidential nominating caucuses are run by state political parties, not the state, and the Trump-friendly Nevada Republican Party decided to stick with a caucus on February 8th. Party leaders viewed a caucus as helping Mr Trump, because of his superior ground game in the state.
In a visit to Nevada last week, Mr Trump urged voters to ignore Tuesday's primary and to only vote in Thursday's caucus.
Mr Trump is close to clinching the Republican presidential nomination after back-to-back wins in Iowa and New Hampshire, and he and Mr Biden are setting their sights on each other ahead of a likely general election rematch in November.
Opinion polls
Ms Haley is vowing to stay in the Republican nominating race and on to a potential last stand in her home state of South Carolina on February 24th, but she has no clear path to the nomination. She trails Mr Trump badly in South Carolina according to opinion polls.
Mr Biden campaigned in Nevada on Sunday and Monday. He will appear on the ballot along with self-help author Marianne Williamson and other lesser-known Democratic challengers. US representative Dean Phillips of Minnesota missed the filing deadline and won't appear on the ballot.
Despite what look like foregone conclusions in Nevada's nominating contests, it will be a hotly contested battleground state because its population can swing to either party and play a decisive role in November's presidential election.
In 2020, Mr Biden narrowly beat Mr Trump in Nevada by 2.4 percentage points. Opinion polls show a likely rematch between Mr Biden and Mr Trump in the swing state will be close.
About 30 per cent of Nevada's population is self-described as Latino or Hispanic on the US Census, and Republicans are making some inroads with these voters nationwide.
Nevada also has many potential swing voters: there are 768,000 registered as "non-partisan", more than those registered as either Democrat or Republican, according to the latest state figures.
