Stock up on sleep and buy a case of Mountain Dew, because we could be in for a long election night.

As the most fascinating, frustrating, and even gut-wrenching election cycle comes to a close, a long, drawn-out conclusion seems like a fitting end.

Just when it looked like former Secretary of State Hillary Clinton was pulling away in the race for the White House, wealthy reality show host Donald Trump inched closer in the final days and even put Clinton’s Electoral College advantage in some doubt.

The competitive presidential race has given Republicans a chance to retain their majority in the Senate, in spite of Trump’s baggage and a map that put them on the defensive in all but one state.

And while the GOP House majority is not in doubt, the size of Democratic gains will impact the size of the Republican Conference in the next Congress and affect Speaker Paul D. Ryan’s ability to lead his party and legislate.

With nearly a dozen competitive presidential states, eight states that will decide Senate control, and a few dozen House races, it’s hard to follow them all as polls close and races are called Tuesday evening. So here is a guide for when and where to focus your attention on election night.

Election night also has a way of testing our patience. It can be the ultimate case of “Hurry up and wait.”

Even though we’ve organized key races chronologically, it may be hours after the polls close before a winner is projected.

For example, in 2012, The Associated Press didn’t call North Carolina for Mitt Romney until almost 11 p.m., even though polls close at 7:30 p.m. in the Tar Heel State. The AP didn’t call Pennsylvania and New Hampshire, where polls close at 8 p.m., until nearly 10 p.m. And it was four days before the AP called Florida.

In the Senate, a handful of races could be too-close-to-call on election night and could even require recounts that stretch the outcome for another few days or weeks. And considering each competitive race is important, any outstanding race could delay when the majority is decided. In addition, runoff provisions in Georgia and Louisiana could complicate how control is called and determined by media outlets Tuesday night.

Republican Sen. Johnny Isakson is likely to win re-election in Georgia, but if he falls short of 50 percent, he moves on to a Jan. 10 runoff, according to state law. And in Louisiana, the top two candidates will move on to a Dec. 10 runoff, which could feature a candidate from each party.

Democrats haven’t expressed any interest in contesting either state, but if control of the Senate is on the line, it’s hard to imagine the party and almost-Majority Leader Charles E. Schumer just walking away.

In the guide and tonight, we’re focusing our coverage on the fights for the Senate and House and introducing readers to the new members. Be sure to sign up for email alerts at the bottom of RollCall.com and download our mobile app in the App Store or on Google Play to be notified when a winner is called in the most competitive races and when new members are elected in the safe races. 

(All times Eastern)

7 p.m.

Indiana Senate

Democrats thought they would win this race from the moment former Sen. Evan Bayh unexpectedly became a candidate in July. Things haven’t worked out that way: The longtime pol has been accused of no longer being an Indiana resident, of spending big money on taxpayer-funded planes, and committing to an active job search before he even left office in 2010. If GOP nominee Rep. Todd Young wins this race — and polls suggest the contest is a dead heat — Republicans will rejoice over snatching victory from the jaws of defeat. 

Virginia’s 10th District

A swing district at the presidential level, freshman Republican Barbara Comstock’s seat was always going to be a Democratic target. She didn’t take a stand on Trump until October, when she was among the first congressional Republicans to call on him to step aside as the nominee. It’s still a Tilts Republican seat, but if Democratic recruit LuAnn Bennett defeats Comstock in this wealthy, well-educated suburban Washington, D.C., district, it’ll be a sign that independent and moderate voters are applying their dislike for Trump to down-ballot Republicans. Another district to watch in this category is Pennsylvania’s 8th, a wealthy suburban district that’s a tossup race.

7:30 p.m.

North Carolina Senate

Republican officials think Sen. Richard M. Burr has run a lackluster campaign, much to their frustration. But the incumbent’s opponent, former state lawmaker Deborah Ross, has watched her poll numbers drop amid a series of hard-hitting attacks that concentrated on her tenure as head of the North Carolina affiliate of the American Civil Liberties Union. This is one of many close races on the map, but it appears to be trending in the GOP’s favor. If Ross wins, expect a big night for Democrats. 

8 p.m.

Pennsylvania Senate

GOP strategists say that Sen. Patrick J. Toomey has run the best campaign of any Senate Republican incumbent (with the exception of GOP Sen. Rob Portman of Ohio). The question he faces, like a lot of Republicans, is whether he can overcome Trump’s expected poor performance in the state. Polls suggest that Democratic nominee Katie McGinty is running slightly ahead of the Republican incumbent even as Clinton runs well ahead of Trump. If Toomey does manage to pull out a victory, he may very well block the Democrats’ path to a Senate majority.  

New Hampshire Senate

Officials in both parties predicted a tight race when Democratic Gov. Maggie Hassan decided to take on Republican Sen. Kelly Ayotte. They were right: No Senate contest has been more consistently competitive than this Granite State battle, with most polls showing a de facto dead heat for the better part of the last 18 months. That makes this race, along with Pennsylvania, a good bellwether. If Democrats win, they are likely on their way to a majority; if Republicans win, they’ll feel great about holding their majority. 

Missouri Senate

Even Republicans readily acknowledge that Democratic nominee Jason Kander is the best Senate candidate in either party this cycle. The 35-year-old Missouri secretary of State has run as an outsider against Republican Sen. Roy Blunt, tapping into the same anti-Washington sentiment that has fueled Trump’s rise. Polls show Blunt retains a small lead, and Missouri is a red state, so he’s still a slight favorite on Election Day. But if Kander wins, it’ll be a sign that 2016 was the year of the political outsider, regardless of party. 

Pennsylvania’s 16th District

With longtime GOP Rep. Joe Pitts retiring, Democrats have a chance to disrupt decades of Republican representation in this Lancaster County district. But even for an open seat, it’s a tough pickup opportunity that hasn’t attracted much outside spending. If Clinton posts impressive margins in Pennsylvania and Democrat Christina M. Hartman triumphs over Republican state Sen. Lloyd K. Smucker, it could be an early sign of a Democratic wave down ballot.

9 p.m.

Colorado’s 6th District

Representing a diverse suburban seat, Republican Mike Coffman is a perennial target for Democrats. He’s made Trump-like comments (questioning Obama’s citizenship in 2012), but was early to vocalize his displeasure with Trump this year. Nevertheless, Democrats have spent big trying to tie him to the GOP presidential nominee. A Coffman loss to state Sen. Morgan Carroll may indicate further down-ballot damage for Republicans, regardless of how hard they’ve tried to distance themselves. And if Coffman survives, he’ll likely be credited for reaching out to his diversifying constituency.

Kansas’ 3rd District

GOP Rep. Kevin Yoder’s seat is one of those red, suburban districts that Democrats have tried to put on the map because of the unpopularity of Trump, and in this specific case, Kansas Gov. Sam Brownback. A similar seat is Minnesota’s 3rd District, where Democrats are trying to tie Rep. Erik Paulsen to Trump, who’s deeply unpopular in his district. Democratic victories in either of these lower-tier races would require a wave.

Minnesota’s 8th District 

Down-ballot Democrats need to over-perform Clinton in must-hold seats like Minnesota’s 8th District, a traditionally blue seat where Trump’s brand of populism has resonated with white working-class voters. One of the seats they need to pick up to make even double-digit gains is Maine’s 2nd District, where Trump has enjoyed similar support among blue-collar workers. Victories for Minnesota Rep. Rick Nolan and Maine Democrat Emily Cain require some Trump voters to break for them.

Wisconsin Senate 

Nobody expected GOP Sen. Ron Johnson to be nipping at the heels of former Sen. Russ Feingold this close to Election Day. But the senator, thanks to a campaign that has made him look like the outsider despite his incumbency, has suddenly and unexpectedly gained ground in the polls. The surge has caught the attention of Republican and Democratic outside groups alike, which have made big, last-minute investments in the state. Democrats are still confident Feingold will win, but if he doesn’t, Republicans might be on track for a better night than they could have ever hoped for. 

10 p.m.

Iowa’s 1st District 

Iowa’s 1st District is a pickup opportunity Democrats should have locked down months ago. Whether they’re able to pick off freshman Republican Rod Blum will depend on how well Clinton performs here. President Barack Obama twice carried this district by double digits, and that alone was enough to make Blum, a Freedom Caucus member, vulnerable. But Trump is doing well in this 90 percent white district, which has boosted Blum in his race against Democrat Monica Vernon. Democrats have had to keep spending here, just as they have in Minnesota’s 2nd District and Florida’s 13th District, two other seats that initially looked like easier pickups.

Nevada Senate

Nevada is the GOP’s only chance at winning a Democratic-held seat. Not that Republicans needed extra incentive: They would love nothing more than to send Sen. Harry Reid into retirement on a losing note. GOP officials consider nominee Rep. Joe Heck a strong candidate, while Democrats think Catherine Cortez Masto’s history-making effort (she would be the first Latina to serve in the Senate) gives her an edge. It would be a remarkable achievement if Heck could win over Hispanic voters in the year of Trump — and a welcome sign for a party worried it has permanently alienated these voters.

11 p.m.

California’s 21st District 

With its Hispanic population approaching 75 percent, GOP Rep. David Valadao’s district is always a Democratic target. Valadao fended off a challenge in 2014, defeating Democrat Amanda Renteria (now Clinton’s national political director) by double digits in a good year for Republicans. But his seat is especially a target this year because of Trump. If Democrat Emilio Huerta defeats Valadao this year, he’ll likely have Trump to thank for motivating Hispanics to vote against the GOP down ballot.

California’s 49th District

Defeating former Oversight and Government Reform Chairman Darrell Issa has become a cause celebre for Democrats, much like knocking off New Jersey’s Scott Garrett. Success here would likely require a wave, with moderate, anti-Trump Republicans choosing to buck Issa for Democrat Doug Applegate.