Voting centres have opened across the US for the midterm elections for Congress.
The elections are widely seen as a referendum on Donald Trump’s presidency.
Polls show voters intend to punish Mr Trump’s Republican Party, and they could hand control of both chambers of Congress to the Democrats.
Democrats have firmed up as narrow favourites to win control of both houses of the US Congress in today's midterm elections, according to the US's top political forecasters.
The result would open new pathways for the party to frustrate Donald Trump's agenda in his final two years in office.
Voting is underway across the US, with polls finding many Americans intend to punish Mr Trump's Republican Party over cost-of-living pressures, including higher fuel costs linked to the Iran war.
"I think the results are going to be better than you think," the president told national breakfast television show Fox and Friends in a phone interview, shortly after polls opened.
Many polls say otherwise, with predictions some states that have not elected Democratic senators for decades could flip.
A dog watches people casting their ballots in Brooklyn on Tuesday. ( Reuters: David Dee Delgado )
Growing concerns about corruption have also featured heavily in some surveys.
But many Democrats are wary of putting stock in the forecasts after polls overestimated their fortunes in several recent elections.
Forecasters say the Senate remains a very close contest that cannot be predicted with much confidence.
In Texas, which has not elected a Democrat to the Senate in almost four decades, some polls show the party's candidate James Talarico ahead of his GOP rival.
"Let's show the world why you should always bet on the underdog," Mr Talarico, who like other Democrats has made pocketbook issues and cleaning up politics central to his campaign, wrote in a social media post on Tuesday.
In a taco restaurant in San Antonio, patrons were split on whether to vote red or blue.
"James Talarico seems to do a lot more for the people," one woman said. "And so just the stuff that he's talked about, I feel a lot better about voting for him than anybody else."
"I'll vote Ken Paxton [the Republican Senate candidate]. It's not even a lesser-of-two-evils thing," a local man told the ABC. "I can tell you what he stands for."
America's political microscope has been on Texas ahead of the midterms. ( ABC News: Cameron Schwarz )
To win the Senate, Democrats must win four seats currently held by Republicans without losing any of their own.
The respected Cook Political Report rates six Senate seats, which are all currently held by Republicans, as toss-up contests: Alaska, Iowa, Kansas, Maine, Ohio and Texas.
But the Republican-held seat in North Carolina is forecast to fall into Democratic hands.
And the Democrat-held Michigan was moved from the "toss-up" category to "leans Democrat" on election eve, despite an eleventh-hour controversy caused by party infighting in that state.
"While Senate control could still swing either way, Democrats have the momentum in the final stretch," Cook analyst Jessica Taylor wrote.
Analysts at Sabato's Crystal Ball, at the University of Virginia, favour Democrats to end up with a 53-47 majority in the chamber. But they note "it wouldn't take much" for the numbers to shift in Republicans' favour.
Democrats have been tipped to win a majority in the House of Representatives for months, but their position appears to have improved in recent days.
The Cook report is projecting Democrats should win 230 to 240 House seats, well above the 218 needed to form majority.
Sabato's Crystal Ball predicts a similar outcome.
Donald Trump makes his final pitch to voters in Washington DC. ( Reuters: Jonathan Ernst )
Americans are casting ballots for all 435 seats in the House of Representatives. They are also voting for 35 members in the 100-seat Senate, where senators serve six-year terms. Thirty-six states are also electing governors.
Mr Trump is not on the ballot, but has repeatedly urged voters to "pretend" he is, including at a series of rallies in the days leading up to the midterms.
The strategy is not appreciated by everyone in his party, given his approval ratings have been at record-low levels and continue to decline.
About 50 million ballots have already been cast, with early turnout outpacing the last midterm cycle in each of the major Senate battlegrounds.
Mr Trump is not on the ballot, but has repeatedly urged voters to "pretend" he is, including at a series of rallies in the days leading up to the midterms.
The strategy is not appreciated by everyone in his party, given his approval ratings have been at record-low levels and continue to decline.
"He started out good, but then he messed up getting involved in that war," Debra Simmons said after casting her ballot in Rocky Mount, North Carolina.
She still voted Republican because "they have more common sense", but said she hoped Mr Trump changed his attitude about rising prices.
"It's unfair," said Wallace Cherry, who was handing out Democrat voting material for North Carolina's First Congressional District in Rocky Mount.
The district's boundaries were redrawn last year, reducing the proportion of Black voters and giving the Republican candidate an advantage.
"They're trying to make sure that their vote is counted more than ours," he said.
Overall, Republicans had hoped to win at least 13 redrawn seats, but analysts say that now looks unlikely.
"We're not gonna win all 13 of those redistricted seats," the Republicans' House Whip, Tom Emmer, told Axios last month.
California is the only state where Democrats have enacted a new map, which could help them pick up five extra seats.
