Los Angeles, United States - Voters cast ballots in eight US states for key primary elections on Tuesday, with all eyes on California, where the outcome could swing the balance of power in Congress.
Democrats in the country's most populous state are battling to ensure they come out on top in several congressional districts that voted for Hillary Clinton over Donald Trump in the 2016 presidential election.
However, given the state's unusual election system in which the two top vote-getters move on to the general election in November, regardless of party affiliation, Democrats fear they may give Republicans the upper hand in some districts where they have a glut of candidates.
"The worry is that with so many enthusiastic Democrats running for Congress, the Democrats will split up the Democratic vote and you'll end up with one or two Republicans in the top two slots," said Elaine Kamarck, a senior fellow at the Washington-based Brookings Institution.
"So there's quite a bit of concern that this would backfire and that congressional districts that would elect a Democrat in the end would be given only the choice of Republicans."
- 'Turnout always the uncertainty' -
The race drew huge attention nationwide, especially given how solidly Democratic California has been, but it is unclear whether the high stakes will spur voters to cast ballots.
"Turnout is always the uncertainty in primary elections," said Louis DeSipio, a political science professor at the University of California at Irvine.
"If Democrats are as energised in California as they have been in some other states, they can move into the general election with no viable Republicans running statewide.
"This seems unlikely, but is a possibility."
Officials said tabulating final results for the vote may take several days, or even weeks, given that many of the 19.4 million registered voters are casting their ballots by mail.
There were 27 candidates looking to succeed Democratic Governor Jerry Brown, and more than two dozen looking to replace veteran US Senator Dianne Feinstein.
The race for governor will now be between deputy governor Gavin Newsom, a Democrat, and Trump-backed Republican John Cox, a businessman who is not well known, according to results published late Tuesday on the state government website.
In the end Feinstein survived and will be on the ballot for the midterm elections in November, results showed.
Newsom is seen as the likely favorite in November.
"I will do anything to fight Trump," Arthur Aguirre, a 76-year-old artist, said at a polling station in Hollywood. "He is destroying our democracy."
And in the race for California's 53 seats in the US House of Representatives, the slate of candidates featured a plethora of novice Democrats looking to make a statement against Trump.
Kamarck said that although Democrats in the most prominent anti-Trump state in the country would be expected to fare well, the "jungle" format of the election could create chaos.
- 'High Crime Nancy Pelosi' -
Trump tweeted early Tuesday urging Republicans to head to the polls.
"Get the vote out in California today for Rep. Kevin McCarthy and all of the great GOP candidates for Congress. Keep our country out of the hands of High Tax, High Crime Nancy Pelosi," Trump said, referring to the 78-year-old House Democratic minority leader.
In the race for the governor's mansion, former San Francisco mayor Newsom -- who gained attention for allowing same-sex unions before the legalisation of gay marriage -- has a strong lead in opinion polls leading up to Tuesday's voting.
In the House races, Democrats are focusing on seven districts currently in Republican hands that voted for Clinton in 2016 and could flip again this year.
But in at least five of them, progressive candidates could split the vote, leaving a path for Republicans to make the November runoff.
The Democratic Party "tried to winnow out some of the candidates, but the same excitement and energy that led them to run in the first place makes them unlikely to listen to the national party," DeSipio said.
Nationwide, Democrats must clinch at least 23 seats from Republicans to wrest control of the House of Representatives.
Apart from California, voters also cast ballots Tuesday in Alabama, Iowa, Mississippi, Montana, New Jersey, New Mexico and South Dakota.