WASHINGTON (AP) — Voters in the key swing state of Nevada head the polls for the second (or, in some cases, third) time this year to select the candidates who will appear in some of this fall’s most competitive legislative races.

After holding both presidential primaries and a presidential caucus in February, Nevadans will vote in primaries for Congress and the state legislature on Tuesday. The state’s congressional delegation is currently composed of five Democrats and one Republican. Tuesday’s marquee races include the Republican primaries for Senate and in the three Democratic-held congressional districts.

First-term Sen. Jacky Rosen, whose seat will likely be among those key to determining the balance of power in the Senate come fall, faces two Democratic challengers in program manager Troy Walker and taxpayer advocate Mike Schaefer. She has significantly outraised her current and prospective opponents, with more than $10 million on hand. The next-best-funded candidate, Republican Sam Brown, has raised $7 million this cycle and spent $4.6 million of it.

Brown, an army veteran who unsuccessfully sought the nomination for Senate in Nevada last cycle, and former Ambassador to Iceland Jeff Gunter are the only two Republican candidates for Senate to have raised at least $1 million. Brown has more party support, with endorsements from the state's Republican Gov. Joe Lombardo and backing from the National Republican Senatorial Committee. The crowded field also includes Jim Marchant, a prominent supporter of former President Donald Trump and promoter of the false narrative around fraud in the 2020 election. Trump has not yet endorsed a candidate in the race.

There are also key races for Nevada’s 1st, 3rd and 4th congressional districts on the Republican side. Those three districts all include at least some of Clark County, home to Las Vegas, and are currently represented by Democratic incumbents Dina Titus, Susie Lee and Steven Horsford. The incumbent in the 2nd District, Mark Amodei, faces a poorly funded challenger and Democrats are not fielding a candidate in the conservative district.

The 1st is considered the safest for the incumbent, as Titus is the longest-tenured Democratic representative in the state and had one of the larger margins of victory in 2022 at 6 percentage points. Still, that hasn’t stopped business owner Flemming Larsen from loaning his campaign $1.5 million. The field also includes Mark Robertson, a retired army colonel who lost to Titus in 2022.

There are seven Republicans seeking the nomination in the 3rd District, which is potentially the state’s most competitive race. The leading fundraiser is former Nevada State Treasurer Daniel Schwartz. His opponents include former state Sen. Elizabeth Helgelien, who’s pitching herself as a strong Trump supporter with endorsements from Marchant and Trump advisers Roger Stone and Michael Flynn.

The 4th District has the smallest field, with just three candidates. Financial adviser and veteran David Flippo has narrowly outspent former North Las Vegas Mayor John Lee. Lee also previously served in the state legislature as a Democrat — he switched his party affiliation to Republican in 2022. Flippo sought a state assembly seat in 2022 but fell short in the Republican primary.

Here’s a look at what to expect on primary night:

The Nevada state primary will be held Tuesday. Polls close at 10 p.m. ET.

The Associated Press will provide vote coverage and declare winners in 43 contested primaries for Senate, House, state Senate, state Assembly and Washoe County commissioner. The key races are both Democratic and Republican primaries for Senate as well as Republican primaries for the 1st, 3rd and 4th House districts.

Registered party members may vote only in their own party’s primary. In other words, Democrats can’t vote in the Republican primary or vice versa. Nevada also has same-day registration, which allows new voters to register at the polls on Tuesday or during the early voting period.

The most important county in statewide elections – and most congressional races — is Clark County, which is home to almost 3 in 4 of Nevada’s residents. The 1st and 3rd districts fall entirely within Clark, while the 4th includes the northern suburbs of Las Vegas plus at least part of five other counties.

Nevada is generally among the slower-counting states. Every voter in Nevada automatically receives a ballot by mail, unless they opt out, and county officials will accept mail ballots up to four days after election day provided they are postmarked on or before election day. Since mail ballots will continue to arrive until June 15, a close contest in which the number of mail ballots could impact the outcome could delay a race call.

This year, the secretary of state has encouraged counties to start tabulating in-person election day votes and mail ballots that arrive before election day during the early voting period. These recommendations are intended to lead to the release of more results faster. Early voting started May 25 and ended June 7.

Regardless of how many ballots are tabulated at poll close, Nevada will not release any results until the final voter in line at poll close has cast their ballot. Because of this rule, the state will often need at least an hour after polls close to ensure everyone has a chance to vote before releasing initial results.

Ballots include a “none of these candidates” option (a selection that Republican voters made at a notable scale in the February presidential primary). However, in the event that the top vote-getter in a primary is “none of these candidates,” the second-highest vote-getter would advance to the general election, and AP would therefore declare that candidate the winner.

The AP does not make projections and will declare a winner only when it’s determined there is no scenario that would allow the trailing candidates to close the gap. If a race has not been called, the AP will continue to cover any newsworthy developments, such as candidate concessions or declarations of victory. In doing so, the AP will make clear that it has not yet declared a winner and explain why.

Nevada does not have an automatic recount law, but candidates may request and pay for a recount within three days of the county or statewide canvass.

As of Jan. 1, there were 2,278,385 registered voters in Nevada. Of those, 31% were Democrats, 28% were Republicans and 34% were independent.

In the presidential primary in February, turnout was 19% of about 703,000 registered voters in the Democratic primary and 13% of about 639,000 registered voters in the Republican primary. Nevada Republicans held both a primary and a caucus in February, and while registered Republicans could vote in both, Trump only filed for the caucuses. About 90% of Democratic votes and 85% of Republican votes in the primary elections were cast by mail or before election day.

In addition to a one-week in-person early voting period, all registered voters in Nevada are sent a primary ballot by mail, unless they opt out. As of June 5, a total of 188,846 people had cast ballots before Election Day. About 45% were cast in the Democratic primary and 40% in the Republican primary.

In the Feb. 6 presidential primaries, the AP first reported results at 11:37 p.m. ET, or one hour and 37 minutes after polls closed. The election night tabulation ended at 4:36 a.m. ET with about 84% of total votes counted.

As of Tuesday, there will be 147 days until the November general election.