With 100 percent of precincts reporting, Balderson had a 1,754-vote lead over O'Connor, with more than 202,000 votes cast.
The race had been closely watched as key test of Republican fortunes in prosperous traditionally conservative suburbs where voters have soured on Donald Trump.
In Ohio, the president took credit for Republican Troy Balderson's performance, calling it "a great victory, " even though the contest could be headed to a recount.
Pollsters rate the OH race between Republican State Senator Troy Balderson and Democratic lawyer Danny O'Connor, 31, as a toss-up. Debbie Stabenow. Trump endorsed James, who also had support from many in the GOP establishment in his race against self-funding venture capitalist Sandy Pensler.
"If you have a real blue wave - if you have the sort of wave, the late break that happened in 2006 where Democrats, from this point, they were ahead in the generic ballot, but they gained 6.6 percent between this point in 2006 and the Election Day - that will give the Democrats the Senate", he added. Strong on Crime, Border & Military.
Governor Asks for Federal Aid as State Battles 17 Wildfires
The fires have killed at least eight people, stretching the state's funds and resources thin as firefighters try to gain control. The Bee reports that a mandatory evacuation order was issued for the area, including all campgrounds and homes.
Should the polarizing Kobach win the primary, some Republican operatives fear he could lose the governor's seat to Democrats this fall.
Laura Kelly will have a tough battle in the Republican stronghold of Kansas, but if she faces Mr Kobach she could play on his extremist profile to target centrist Republicans. It's an enormous amount of exposure for their party and we don't see that for the Republican party. A win for Democrats here on Tuesday would signal further danger for Republicans in the fall.
However, if Balderson keeps the victory, it will be short-lived - the seat will go up for election again in November for the general midterm election. Check back for updates throughout the evening as votes are counted.
The pro-Balderson effort has focused largely on motivating Republican voters by casting O'Connor as extreme.
O'Connor needed Franklin County - which includes the state capital of Columbus - to come out strongly for him in order to topple his Republican rival.
O'Connor and his Democratic allies railed against the tax plan, casting it as a giveaway for the rich that exacerbates federal deficits and threatens Medicare and Social Security.
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But this isn't the first time the 25-year-old's future at Old Trafford has been in doubt. I think the World Cup is the flawless habitat for a player like him to give the best.
"A Republican loss well might tell us more".
The special election will fill the seat vacated by Rep. Patrick Tiberi (R), who is retiring.
Iraq War veteran John James also won the Michigan GOP Senate primary to take on Democratic Sen.
Senate contests in Missouri and MI will come into focus as two vulnerable Senate Democrats, Missouri's Claire McCaskill and Michigan's Debbie Stabenow, are expected to easily claim their party's nominations. He'd join Sen. Tim Scott as the only black Republican senators if he did.
Trump himself campaigned at Balderson's side just 72 hours before Election Day, a weekend appearance to help energize his loyalists in a district the president carried by 11 percentage points.
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Meghan's dad, 74, had given a string of damaging media interviews after she and the royals completely cut all contact. According to Hello Magazine, the Duke and Duchess of Sussex have adorable nicknames for each other.