Republicans are clinging to a razor-thin lead in Ohio’s hotly contested House special election.

It was a race the GOP had expected to win easily but that ended up demonstrating the high level of Democratic enthusiasm ahead of the midterm elections in November.

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The race in Ohio's 12th District was too close to call as of late Tuesday night, with Republican state Sen. Troy Balderson leading Democrat Danny O’Connor by less than a percentage point. At least 3,367 provisional ballots were yet to be counted, making the outcome unknown, potentially for days.

Republicans may have avoided an electoral disaster, but the closeness of the race provided ominous signs for the party as it looks to hang on to its 23-seat majority in the House in November.

Meanwhile, female candidates swept the field in other races on Tuesday, providing more signs that 2018 could indeed end up the “Year of the Woman.” And the ultimate impact of President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE's endorsements — and of progressive stars Sen. Bernie Sanders Bernie SandersThe Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power Bernie Sanders: 'This is an election between Donald Trump and democracy' The Hill's 12:30 Report: Trump stokes fears over November election outcome MORE (I-Vt.) and Alexandria Ocasio-Cortez — in various races proved to be uncertain.

Here are the key takeaways from Tuesday’s races:

GOP leads, but Dems see bright spots

O’Connor may be down, but the Democrats are not out.

Democrats were able to make a genuine contest for a seat that has been in Republican hands for decades, showing further signs that Trump may be struggling with suburban voters in Ohio's 12th District.

Also helping: Democrats recruited a young candidate who campaigned hard and sought to appeal to moderate voters, without demonizing Trump — a similar strategy that Rep. Conor Lamb (D) used to win a special House election in Pennsylvania in March.

Republicans sought to make House Minority Leader Nancy Pelosi Nancy PelosiPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' On The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline Trump signs largely symbolic pre-existing conditions order amid lawsuit MORE (D-Calif.) a key issue in the campaign, trying to closely tie O'Connor to her, but the Democrat appears to have been largely able to overcome the attacks and keep the race close, despite an MSNBC interview in which the candidate admitted he would ultimately support whomever the party nominated as leaders.

GOP may be in genuine trouble in the suburbs

The race showed Republicans may have a potential problem on their hands in suburban districts.

Democrats are targeting well-educated voters and women residing in the suburbs who have historically backed Republicans but who are frustrated with the president and want members of Congress who will be a check on him.

There are 68 other GOP-held seats that are more favorable for Democrats than Ohio's 12th District. Of those seats, Trump won 45 by a smaller margin than in Ohio. And the other 23 seats are held by Republicans but won by Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonFox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio Trump, Biden court Black business owners in final election sprint The power of incumbency: How Trump is using the Oval Office to win reelection MORE in the 2016 election.

Democrats are playing in a large swath of those seats, which are more than enough to target in their battle to take back the House this fall. Many of those seats are also in suburbs outside of a bigger city, particularly in the Midwest and Rust Belt. They’ll have to continue playing heavily in those types of districts if they want a shot at taking back the House.

Trump's impact on election remains uncertain

Trump was quick to claim credit for Balderson's too-close-to-call victory on Tuesday after appearing at a last-minute campaign rally. Though his visits can boost the Republican base, it remains to be seen how helpful — or hurtful — they can be in attracting more moderate and suburban voters.

Furthermore, Trump also has shown a willingness to back more extreme candidates than even his fellow Republicans had been hoping for, raising concerns about their prospects in the fall.

Trump appeared to do well in Michigan, where military veteran John James, whom Trump effusively endorsed, prevailed over his GOP primary opponent in a Senate race. James offers a compelling story as a black Republican candidate running for a body that counts Tim Scott Timothy (Tim) Eugene ScottAuthor Ryan Girdusky: RNC worked best when highlighting 'regular people' as opposed to 'standard Republicans' Now is the time to renew our focus on students and their futures GOP lobbyists pleasantly surprised by Republican convention MORE (R-S.C.) as its sole black GOP senator.

But Trump also endorsed Secretary of State Kris Kobach, a conservative firebrand, over incumbent Gov. Jeff Colyer in Kansas's gubernatorial primary. The race remained too close to call. But if Kobach prevails, he could face tough odds in the general election, even in red-state Kansas.

But Sanders's and Ocasio-Cortez’s influence is also unclear

Sanders's and Ocasio-Cortez’s forays into the primaries were greeted with much fanfare.

But in Michigan, their choice for governor, Democrat Abdul El-Sayed, ultimately fell to Gretchen Whitmer (D), a former Democratic leader in the state Senate. Likewise, the Ocasio-Cortez-backed Democrat in Missouri’s 1st District, Cori Bush, failed to edge out longtime incumbent Lacy Clay William (Lacy) Lacy ClayFive things we learned from this year's primaries Progressives aim for big night in Massachusetts Progressives look to unseat top Democrat in Massachusetts primary MORE in his primary.

Sanders and Ocasio-Cortez, the 28-year-old democratic socialist who beat out Rep. Joseph Crowley (D-N.Y.) in her House primary in June, have become standard-bearers for the progressive movement — and Democrats have been eyeing what kind of impact they will have in primaries this year.

Questions also linger beyond the primaries, given doubts about whether their message will resonate with voters in more rural and suburban parts of the country, particularly in the Midwest.

Another candidate backed by the duo in Democratic House primary for Kansas’s 3rd District, Brent Welder, slightly led challenger Sharice Davids early on Wednesday, though the race was far from being called.

But both Davids and Welder campaigned as progressives, posing a key test of whether policies such as "Medicare for all" can win over Kansas voters in a tough race against incumbent Rep. Kevin Yoder Kevin Wayne YoderBottom line Amanda Adkins wins GOP primary to challenge Rep. Sharice Davids Sharice Davids to vote for Trump impeachment articles: 'The facts are uncontested' MORE (R) in the fall.

Another strong night for women

The “Year of the Woman” theme continued on Tuesday as more female candidates notched primary victories in crowded contests. That was particularly true in Michigan in races up and down the ballot.

Whitmer roared to victory in Michigan’s gubernatorial primary. Whitmer, who held a substantial financial edge, defeated two male opponents who sought to run to the left of her.

In two competitive House seats in Michigan, Democrats Gretchen Driskell and Elissa Slotkin cruised to victory in their races. Both are considered top recruits by national Democrats as they go on to face GOP Reps. Tim Walberg Timothy (Tim) Lee WalbergThe health care crisis no one is talking about Overnight Defense: Pentagon policy chief resigns at Trump's request | Trump wishes official 'well in his future endeavors' | Armed Services chair warns against Africa drawdown after trip GOP chairman after Africa trip: US military drawdown would have 'real and lasting negative consequences' MORE and Mike Bishop, respectively.

While the race is too close to call in both primaries for retiring Rep. David Trott’s (R-Mich.) seat, the Democratic and Republican nominees are likely to both be women.

With 86 percent of precincts reporting, Republican Lena Epstein, a staffer on Trump’s Michigan campaign, was ahead of her closest competitor by 6 points. And on the Democratic side, Haley Stevens, who was endorsed by Clinton, holds a small lead.

And in the race to replace former Rep. John Conyers John James ConyersBiden's immigration plan has serious problems Tlaib wins Michigan Democratic primary Tlaib holds lead in early vote count against primary challenger MORE Jr. (D-Mich.), former state Rep. Rashida Tlaib (D) secured the nomination in a heavily Democratic seat. That means she’ll likely become the first Muslim woman elected to Congress.

And in Washington state, women also look poised for victories in two top House races.