Voters in five states are heading to the polls on Tuesday to cast their ballots in several races that could send some of the clearest signals yet about the political mood heading into the November midterms.

One of the key races to watch Tuesday night is the special election in Ohio’s 12th District, where Democrat Danny O’Connor and Republican Troy Balderson are locked in a heated battle to replace retired Rep. Pat Tiberi Patrick (Pat) Joseph TiberiOhio New Members 2019 Many authors of GOP tax law will not be returning to Congress GOP Rep. Balderson holds onto seat in Ohio MORE (R).

While both candidates are already on the ballot in November for a rematch to win a full two-year term, Tuesday's special election carries major implications for Republicans seeking to hold control of the House and Democrats trying to retake the chamber.

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Ryan congratulates Balderson

11:41 p.m.

House Speaker Paul Ryan Paul Davis RyanKenosha will be a good bellwether in 2020 At indoor rally, Pence says election runs through Wisconsin Juan Williams: Breaking down the debates MORE (R-Wis.) is congratulating Balderson on his win in Ohio's 12 District, even as the race remains too close to call.

Congrats to @Troy_Balderson on his win in the #OH12 special election tonight," Ryan tweeted. "Looking forward to working with him to build on our accomplishments this fall.

Congrats to @Troy_Balderson on his win in the #OH12 special election tonight. Looking forward to working with him to build on our accomplishments this fall. — Paul Ryan (@PRyan) August 8, 2018

Balderson and Trump have already declared victory in the race. But O'Connor has yet to concede, and polls show Balderson leading by less than 1 point with 100 percent of precincts reporting. The AP has yet to make an official call in the race.

Balderson declares victory over O'Connor

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11:16 p.m.

Balderson is declaring victory in Ohio's 12th District.

Speaking to supporters, Balderson thanked Trump, Vice President Pence and retired Rep. Pat Tiberi (R-Ohio), and said that he looked forward to running against O'Connor once again in the fall.

"Tonight I’m going to promise to you that I’m going to work relentlessly – relentlessly for this 12th congressional district," Balderson said. "America is on the right path and we’re going to keep it going that way."

"It’s time to get to work," he continued. "Over the next three months, I’m going to do everything I can to keep America great again."

O'Connor speaks to supporters with race too close to call

11:10 p.m.

O'Connor isn't conceding to Balderson in the special election for Ohio's 12th District.

The Franklin County recorder addressed supporters as polls showed a slight lead for Balderson with 100 percent of precincts reporting. But despite the apparent loss, O'Connor called the race a "tied ballgame" and touted how close he and Balderson were in the vote count.

"Can you believe how close this is?" O'Connor said. "We are in a tied ballgame and you made this possible."

With all precincts reporting, Balderson carried 50.2 percent of the vote, while O'Connor came in at 49.3 percent. That's an especially tight margin considering Trump won the district in 2016 by about 11 points.

Laura Kelly wins Kansas Democratic gubernatorial primary

10:34 p.m.

Democrat Laura Kelly has secured the Democratic nomination for Kansas governor, overcoming a crowded field of Democratic hopefuls in the party's primary.

The Kansas state senator won the primary on Tuesday with just under 52 percent of the vote, according to the AP. Her closest challenger, former Wichita Mayor Carl Brewer, came in second with a little under 22 percent of the vote.

On the Republican side, the race was a dead heat with Secretary of State Kris Kobach trailing incumbent Gov. Jeff Colyer by less than 1 percent.

10:10 p.m.

In one of the most unusual primaries, two candidates - both named Ron Estes - faced off in Kansas' Republican primary in the 4th District.

And it was Rep. Ron Estes (R-Kan.) who vanquished his Republican primary challenger Ron Estes.

The incumbent Estes was widely expected to win the primary. At the time the AP called the race, Rep. Estes had taken nearly 81 percent of the vote, compared to his opponent's 19 percent.

Gretchen Whitmer wins Democratic gubernatorial primary in Michigan

10:05 p.m.

Former state Sen. Gretchen Whitmer has defeated Abdul El-Sayed, a former director at Detroit Health Department, and businessman Shri Thanedar in Michigan's Democratic gubernatorial primary. The win sets her up to face off against Republican state Attorney General Bill Schuette in November.

Whitmer had taken 50 percent of the vote by the time the AP called the race, putting her about 15 points ahead of El-Sayed and nearly 35 points ahead of Thanedar.

Ohio special election still neck-and-neck, raising prospect of recount

9:55 p.m.

O’Connor and Balderson are nearly tied, with 85 percent of precincts reporting. The Ohio Democrat holds a 155-vote lead. Most counties have fully reported, meaning it will likely come down to what happens in one of the most competitive parts of the 12th district: Delaware County.

If the race remains this close, it could very wll trigger a recount. Ohio election law stipulates that if the margin is less than 0.5 percent, there will be an automatic recount.

Read more about Ohio’s recount rules here.

McCaskill, Hawley set to face off in Missouri Senate seat

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9:40 p.m.

Schuette wins GOP governor's primary in Michigan

9:35 p.m.

Michigan Attorney General Bill Schuette has won the Republican gubernatorial nomination, according to Associated Press.

With 18 percent of precincts reporting, Schuette held 51 percent of the vote, overcoming Republican challenger and Lt. Gov. Brian Calley, who had only about 24 percent of the vote at the time AP called the race.

It's not yet clear which Democrat Schuette will face in November, but former state Sen. Gretchen Whitmer is currently leading the pack with about 49 percent of the vote.

Ohio district shows neck-and-neck race so far

9:25 p.m.

With 74 percent of precincts reporting, Ohio's special election is neck and neck. O’Connor is still ahead, but leads Balderson by less than a point.

Both candidates appear to be doing well in their geographical bases, with O’Connor running up the score in Franklin County and Balderson overperforming in Zanesville and Newark

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Meanwhile, Morrow County has finished reported and Balderson won by about 40 points, or 70 percent to 29 percent. Election forecaster Dave Wasserman of Cook Political Report says that Balderson is on track there, predicting that he needed 69 percent of the votes.

And Balderson doing well in Licking County with Election Day voting and is pretty much on track with Trump’s 2016 numbers.

All precincts have reported in Marion County, Ohio

9:00 p.m.

Balderson emerged victorious in Marion County – the smallest in Ohio's 12th District – finishing with just under 68 percent of the vote.

But O'Connor made a decent showing in the country, ending the race there with just under a third of the vote.

Tight race in Kansas gubernatorial primary

8:50 p.m.

With early voting in, it looks like a tight contest between incumbent Gov. Jeff Colyer and Secretary of State Kris Kobach in Kansas’s GOP primary for governor.

Colyer holds a 2-point lead over Kobach — but again, it’s still very early in the night.

The race became even more interesting when Trump offered a last-minute endorsement of conservative firebrand Kobach a day before the primary, a move that frustrated Republicans who worry a Kobach victory could hand the race to Democrats in November.

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On the Democratic side, state Sen. Laura Kelly holds an early lead over her four other primary competitors.

Meanwhile, the other race to watch in Kansas’s 3rd congressional district still has no updates.

Early results filter in from Michigan

8:45 p.m.

Early results are coming in from Michigan, where former state Sen. Gretchen Whitmer is leading Abdul El-Sayed and Shri Thanedar in the state's Democratic gubernatorial primary.

El-Sayed, a former Detroit Health Department director, holds a slight lead in Washtenaw County, where up-and-coming Democratic star Alexandria Ocasio-Cortez and Sen. Bernie Sanders (I-Vt.) campaigned for him in recent weeks.

Whitmer has led both El-Sayed and Thanedar in recent opinion polls. But El-Sayed has touted endorsements from some of the country's most prominent progressives in his bid to overcome those polling numbers.

Polls close in Kansas and Missouri

8 p.m.

Polls have closed in Kansas and Missouri, where Republican Attorney General Josh Hawley is expected to secure his party's nomination to challenge Sen. Claire McCaskill (D).

O’Connor leads Balderson in early voting

8:00 p.m.

All of the ballots from early voting are in and O’Connor maintains his lead over Balderson, 62.9 percent to 36.4 percent — though these are very preliminary results.

The early tallies haven’t brought many surprises so far. Democrats went into Tuesday with an early voting advantage, but Republicans will likely close that gap from Election Day voting.

O’Connor ran up the score his home base of Franklin County, and Balderson also did well in his area of Muskingum County.

O'Connor (D) wins Richland Co. absentees 54%-45%. Balderson (R) wins Morrow Co. absentees 55%-45%. Nothing really unexpected so far. #OH12 — Dave Wasserman (@Redistrict) August 7, 2018

Balderson (R) wins Muskingum Co. early vote 61%-38%. That's a sign he's getting a good hometown bonus. O'Connor (D) will need to post big numbers in Delaware/Franklin to make up for it. #OH12 — Dave Wasserman (@Redistrict) August 7, 2018

First Ohio results show O'Connor leading

7:47 p.m.

The first results from Ohio are coming in, showing O'Connor with an outsized lead over Balderson.

A word of caution: Most of the early votes counted so far are from Franklin County – O'Connor's home turf – meaning the wide lead is unlikely to hold.

Early results from Licking County give Balderson a slight edge over O'Connor, and in Marion County, the Republican is leading by about 26 points.

Polls close in Ohio

7:30 p.m.

The first polls of the night have closed in Ohio. The New York Times estimates that the first results of the special election will roll in around 7:45 p.m.

The next polls that will close are at 8 p.m. in Kansas and Missouri, where the big primaries to watch will be the Kansas governor’s race and Kansas’s 3rd district.

Gubernatorial primaries in Kansas and Michigan could also provide some insight into President Trump’s endorsing power and the strength of progressives’ message in states won by the real estate mogul in 2016, particularly in the Midwest.

Among the other states voting on Tuesday are Washington and Missouri, where Republican Attorney General Josh Hawley is widely expected to secure his party’s nomination to challenge Sen. Claire McCaskill (D-Mo.) for her Senate seat.

Polls close 7:30 p.m. EDT in Ohio, 8 p.m. EDT in Kansas and Missouri, 9 p.m. EDT in Michigan (two time zones), 11 p.m. EDT in Washington. The Hill is providing live updates.