Democrats are showing up to vote in record numbers, but so are Republicans. Trump’s approval rating has remained dismal, but consistent. And the states and districts in which the two parties are fighting for control of Congress are markedly different than what strategists on both sides expected.

Here are the five biggest surprises defining the 2018 midterm elections:

Democrats are in the hunt for Senate control

Ten Democratic senators are running for reelection in states Trump carried in 2016. That alone should have all but guaranteed Republicans would add to their narrow 51-49 majority in the midterms.

Democrats already had strong challengers for Republican-held seats in Nevada and Arizona, but they have bolstered their playing field with surprisingly good recruits in Tennessee and even Texas.

It still remains likely that Republicans will increase their margin in the Senate this year.

But a year ago, the GOP’s chances weren’t even in question. Democrats need to run the table to win back control of the Senate, an unlikely scenario — but one that looks a lot more plausible than it did at the beginning of the cycle.

Bill Nelson is the most endangered Democrat

Sure, Democrats are in the conversation — but that conversation gets a lot more strained if they start losing seats. And the most vulnerable Democrat up this year, the only one who has consistently trailed or tied in public polls, is Nelson.

Nelson faces Gov. Rick Scott (R), who has been spending freely from his considerable fortune on television time since entering the race.

Nelson, meanwhile, focused his efforts on low-key fundraisers and field organizing, forgoing TV spots ahead of Florida’s Aug. 28 primary — a risky move in a vast state where television often makes or breaks campaigns.

Nelson launched his first TV ad a day after the primaries, and Democrats in Washington insist that he is poised to come on strong through the fall.

His allies argue that Scott has yet to surge in the polls despite far outspending Nelson and that a string of Democratic special election victories in the state legislature bodes well for the senator’s chances.

But that hasn’t quelled the concerns of some political observers, who see Nelson running a lackluster campaign against the toughest — and wealthiest — GOP opponent of his political career.

The Cook Political Report currently rates the race as a "toss-up."

But now the pressure is on the Florida Democrat to hold on to his seat in a key swing state that narrowly went for Trump in 2016.

The white whale states

For years, Democrats have salivated over Texas, and Republicans have pined for New Jersey.

O’Rourke’s attention-grabbing campaign has put Cruz on defense in a deep-red state that remains unfriendly territory for Democrats running statewide, despite demographics that look like the state should be moving toward the purple column.

The Democratic congressman called for Trump’s impeachment after his summit with Russian President Vladimir Putin. But arguably O'Rourke's biggest moment in the spotlight is the viral video of him defending NFL players kneeling in protest during the national anthem.

Since then, Cruz and his allies have gone on the attack — and gotten personal, with the Texas GOP tweeting O’Rourke’s mugshot from his decades-old DWI arrest. And Club for Growth is readying a seven-figure ad blitz to buoy Cruz.

Meanwhile, in New Jersey, Menendez is facing some electoral blowback after his corruption case ended in a hung jury, with the charges later thrown away by federal prosecutors. Menendez won just 62 percent of the Democratic primary vote, a shockingly close call for an entrenched incumbent.

Republican Bob Hugin, a former pharmaceutical company CEO and Trump finance chairman in New Jersey, has poured in at least $15 million into the campaign. Polls have shown a tighter-than-expected race, though Democrats believe Hugin's Trump ties and roots in the pharmaceutical industry as the opioid crisis rages on will be liabilities.

But as Democrats step up their anti-corruption messaging against Republicans, the GOP plans to remind voters about Menendez’s own past legal woes.

Texas and New Jersey are white whales for each party — states that seem within reach, but then slip away at the last minute. This year, both sides have launched their Pequods once again.

Some seats are already off the table

Curbelo, who represents increasingly Democratic South Florida, has charted a much more moderate path than the rest of his party on climate change and immigration. He leads his opponent, Debbie Mucarsel-Powell (D), by 7 points — and that was a poll conducted for the Democratic Congressional Campaign Committee.

In Pennsylvania, Fitzpatrick is the one bright spot for Republicans in Philadelphia’s suburbs, where Democrats are poised to make major gains.

Fitzpatrick has carved out a similar portfolio to Curbelo and has won over local labor unions, which typically endorse Democrats. The freshman, who won the seat once held by his brother Mike, faces Scott Wallace, a progressive philanthropist who’s largely self-funded his campaign.

Blum is a perennial Democratic target, and though Trump won his district in 2016, Democrats nominated a young state legislator, Abby Finkenauer, in a cycle where scores of women and young candidates are poised to make history.

In New Jersey, Democrats landed their top pick to succeed LoBiondo, moderate state Sen. Jeff VanDrew. Republicans abandoned their candidate, Seth Grossman, after multiple reports surfaced about him sharing racist stories online.

More governor races are up for grabs

Republicans were always going to be on defense in the race to protect their governorships this year because the party controls so many state executive offices to begin with.

But Democrats have mounted promising challenges to a number of Republican-held seats, in states ranging from swing Ohio, Michigan, Wisconsin, Maine and Iowa to redder Georgia and Arizona.

Even Kansas is at risk after Republicans nominated Secretary of State Kris Kobach (R), an arch conservative, over a more establishment-minded incumbent governor.

Add those to almost-certain Democratic pickups in states like New Mexico and Illinois, where the party’s nominees are running far ahead of Republicans.

Republicans aren’t without their own opportunities, a reminder that voters think differently about their governor than they do about candidates for federal offices.

A three-way race in Alaska, where independent Gov. Bill Walker faces challenges from both major parties, favors the GOP. A deeply unpopular retiring incumbent in Connecticut opens another opportunity for Republicans.

The biggest surprises in the battle over the nation’s governorships, though, may be the incumbents who are not at risk: Democrats reliably win Vermont, Massachusetts and Maryland in presidential elections, but Govs. Phil Scott (R), Charlie Baker (R) and Larry Hogan (R) are all on a glide path toward another term.