Ohio special election - live updates: State wait for exit poll results after Donald Trump Jr and his father back Troy Balderson
Ohio's 12th district is the scene for the last high stakes special election of the season. The race is a key test for President Donald Trump, who will be a key part of the Republican playbook in the 2018 midterms.
Republicans are scrambling to avoid an embarrassing defeat in a seat that the party has held for decades. Mr Trump has backed Republican Troy Balderson, who is facing Democrat Danny O'Connor. A win for Democrats would signal further danger for Republicans in November.
President Trump has also tweeted his support for Tony Balderson and also held a rally for him late last week.
The day's races, like dozens before them, pitted the strength of Trump's fiery supporters against the Democratic Party's anti-Trump resistance. The results will help determine the political landscape — and Trump's standing within his own party — just three months before the GOP defends its House and Senate majorities across the nation.
As well as voters in Ohio, who will send someone to Congress immediately, today also sees primary races in Kansas, Missouri, Michigan and Washington state.
As we wait for the results to come in, follow all the latest updates with our liveblog below.
In Ohio, outgoing congressman Pat Tiberi won the district with a margin of about 37 percentage points in 2016. Today, Emerson, which has published the most recent poll of the battle between Troy Balderson and Danny O'Connor, scores it Balderson 46 and O'Connor 47.
Will be interesting to see turnout tonight. Special elections and primaries often see a pretty low number of voters, but there's evidence some people feel fired up
In addition to the power of Mr Trump's endorsement, pundits will be watching to try and determine whether Alexandria Ocasio-Cortez - the Democrats latest star after she won the primary New York's 14th congressional district - also has it. She has been campaigning for progressives across the country. She's campaigned for James Thompson in Kansas and Abdul El-Sayed in Michigan. Everyone will want to see if she has the power help outsider candidates in areas outside of New York
The most watched race tonight is the special congressional election in Ohio. Republican Troy Balderson is fighting to defeat Democrat Danny O'Connor. Republicans have held the seat for three decades. If Democrats win tonight in the state's 12th congressional district, many will believe it could signal a so-called 'blue wave' in November.
Republicans have been hoping for Democratic discord in Kansas' 3rd Congressional District, a suburban Kansas City district where several candidates were fighting for the chance to take on Republican Rep. Kevin Yoder in November.
The five-way Democratic primary featured labor lawyer Brent Welder, who campaigned recently with self-described democratic socialists Vermont Sen. Bernie Sanders and ascending political star, Alexandria Ocasio-Cortez, a New York congressional candidate.
Also in the race: Native American attorney Sharice Davids and former school teacher Tom Niermann.
Donald Trump Jr has tweeted his support for Troy Balderson, the Republican in Ohio's special election. He's the last of the Trump men to get onboard, with his father and brother tweeting their support earlier today.
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.
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.
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.
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.
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.
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.
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!
Here are the remaining primary elections after today's primaries in Ohio, Missouri, Michigan, Kansas and Washington:
August 11 - Hawaii August 14 - Connecticut, Minnesota, Vermont August 21 - Alaska, Wyoming August 28 - Arizona, Florida September 4 - Massachusetts September 6 - Delaware September 11 - New Hampshire September 12 - Rhode Island September 13 - New York (statewide offices only) November 6 - Louisiana.
