Michigan, Kansas, Missouri and Washington hold primary elections
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Four US states are held primary elections with a fifth having a special House vote. A number of the races were a test for Donald Trump and the amount of sway he holds with voters ahead of crucial midterm elections.
Michigan, Missouri Kansas and Washington had a mixture of governor and senate races, preparing the states for the November polls.
Voters in Ohio's 12th district, where Mr Trump personally stumped for Troy Balderson, were split nearly down the middle, though the GOP hopeful claimed victory in the race to succeed resigning Republican representative Pat Tiberi.
Republicans had scrambled to avoid an embarrassing defeat in a seat the party has held for decades. Mr Balderson faced Democrat Danny O'Connor in the last special congressional election before the midterms. A win for Democrats would have signalled further danger for Republicans in November.
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The GOP previously lost a similar race in Pennsylvania and saw one in Arizona get too close for comfort.
In the Republican race to pick a candidate for Kansas governor, Mr Trump has backed Kris Kobach, a conservative agitator for strict immigration and voter ID laws.
He is facing Kansas Governor Jeff Colyer, who raised more money than Kobach, received the endorsement of the National Rifle Association, brandished his anti-abortion credentials and has the backing of Kansas political legend Bob Dole.
While some White House advisers had reportedly asked the president to stay clear of the race, amid fears Mr Kobach would lose in the midterms, Mr Trump's tweet endorsement could tip the scales in a competitive race, as some other recent Trump endorsements have done. Mr Trump's tweet backing Georgia Republican governor hopeful Brian Kemp vaulted him to an easy primary runoff win two weeks ago. Trump also has recently given a boost to GOP primary candidates in Florida, South Carolina and Alabama.
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Mr Trump also endorsed in two Michigan primaries: state Attorney General Bill Schuette in the gubernatorial contest and John James for Senate.
For the Democrats, the battle between progressive candidates and the establishment will continue on Tuesday. Both Senator Bernie Sanders of Vermont and Alexandria Ocasio-Cortez, a round progressive who surprisingly beat an establishment candidate earlier this summer, have endorsed Abdul El-Sayed, who is running for governor in Michigan, and Brent Welder, who is running in Kansas’ 3rd District. Mr El-Sayed has trailed the establishment-backed Gretchen Whitmer in polling, but progressives are pushing for an upset.
With many of the races too close to call, we will give you all the latest on the elections, with results expected to come in late this evening.
Former Vice President Joe Biden has lent his support to M O'Connor's campaign by recording a robocall in which he told voters they need a leader "like Danny who will stand up for working families."
"Danny's the only candidate on the ballot who will fight to lower the cost of health care, create good jobs and refuse to raise the retirement age for Social Security and Medicare. Electing Danny to Congress puts us one step closer to taking back the House and making sure we have leaders in Washington who will fight for our values -- Ohio values," Mr Biden is heard saying in the recording.
Voters in Kansas will determine just how powerful an endorsement from Donald Trump can be: They're choosing between current Governor Jeff Colyer and current Kansas Secretary of State Kris Kobach – the Trump-backed option – in the Republican gubernatorial primary.
Mr Kobach led the president's ill-fated voter fraud commission last year, and secured an endorsement from Mr Trump just 24 hours before polls opened. The two men appear to be neck-in-neck in the primary race right now – but some Republicans are reportedly worried that Mr Kobach won't be able to hold off a Democratic challenger in November. Stay tuned!
Michigan has another exciting gubernatorial race, this time on the Democrats' side. State Senate Democratic leader Gretchen Whitmer – the establishment favourite – is facing off against up-and-comer Abdul El-Sayed, who's scored the coveted endorsement of progressives like Senator Bernie Sanders and House candidate Alexandria Ocasio Cortez.
Entrepreneur Shri Thanedar is also running, at the same time a stage play based on his life debuts in Detroit.
You can read up here on Fayrouz Saad, whose primary is today in Michigan's 11th. She's a millennial who's worked for the Obama administration – and if elected, she'll be the first Muslim woman in US Congress.
A fun fact about Michigan's gubernatorial primary is that Donald Trump endorsed Attorney General Bill Schuette in the Republican race – in a tweet misspelling his name. The president forgot the "c" in Mr Schuette's last name in his first endorsement attempt, but quickly corrected it.
It doesn't seem to have hurt the attorney general too much, because he's still leading the pack of Republican contenders. Lieutenant Governor Brian Calley is also running, along with state Senator Patrick Colbeck.
Michigan could see its highest primary voter turnout in four decades today, according to the Detroit News. Fifty per cent more Michiganders had requested a ballot last week, and 39 per cent more had returned them, than at the same time in the 2014 primary cycle. Political consultant Mark Grebner told the paper as many as 1.8m people could vote today.
Austin Petersen, a Republican Senate candidate in Missouri whose primary is today, once got kicked off of Facebook for running an AR-15 giveaway as a campaign fundraiser. Read about it here.
A reminder as exit polls start coming in that results in most races won't be finalised tonight. A number of states allow voters to mail in their ballots all the way up until election day, so final results could take days to tabulate. Still, we'll start getting a pretty good picture as polls close around 8pm local time.
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