U.S. election explained: Americans vote for a lot more than just the president on Nov. 8

When Americans head to their local polling stations on Nov. 8, they won't only be choosing the candidate they want as their next president, they'll also be voting for a whole lot more.

Known as "down ballot" races, election day will also usher in new members of Congress, 12 state governors, as well as state and local officials and judges in some jurisdictions.

Here's what you need to know about other races happening on Nov. 8.

Congressional elections

The U.S. Congress is made up of two chambers: the House of Representatives and the Senate. There are 435 seats in the House, which come up for election every two years.

In the Senate, there are 100 seats (two for each state), with each senator serving a six-year term. Those terms are staggered, and every two years, one-third of the seats come up for election.

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Senators belong to one of three "classes" depending on when they were elected. This year is a Class III election, meaning those who were elected in 2010 are up for re-election.

This year, there are 34 Senate seats being contested. Twenty-four of them are currently held by Republicans, the other 10 by Democrats.

Is control of Congress at stake?

Republicans currently hold majorities in both the House and the Senate.

The party is unlikely to lose the House, as Democrats would have to flip 30 seats in order to take control. In the 2014 election, Republicans won 247 seats to the Democrats 188 — the party's largest House majority since 1928. There are currently three vacancies, however, because of the death of one Democratic member and the resignations of one Democrat and one Republican. Democrats are expected to make gains on Nov. 8, but not to win a majority.

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It's a different story in the Senate, which the Republicans took control of in 2014. The party currently holds 54 of the 100 seats. If Hillary Clinton and her running mate Tim Kaine win the race for the White House, the Democrats would need to flip just four seats to effectively achieve a tie in the chamber. (There are currently two independent senators who tend to vote with the Democrats.)

In the event of a tie during a Senate vote, the vice-president gets to cast the deciding vote.

There is plenty of concern among Republicans that the Senate could flip on Nov. 8. Many suggest that their controversial presidential candidate could have an impact on down-ballot races. Some Republican candidates have backed Donald Trump, others have distanced themselves, and still others have tried — with varying degrees of success — to walk a fine line in between.

What does Congress control?

The Constitution lays out specific powers for both chambers, some are shared, some are unique to either the House or the Senate. In general, Congress has the power to: pass bills that go to the president to become law; regulate commerce; declare war; collect taxes; and propose Constitutional amendments. Congress is also in charge of federal budgets. If you've ever heard of a "government shutdown," like the one that happened in 2013, that was because Congress couldn't agree on a budget bill by a certain deadline.

Budget bills must originate in the House — that's one of its unique responsibilities. It also is the chamber that can initiate impeachment proceedings against a president. If the House does agree to try to impeach a president, the proceedings are then carried out in the Senate.

The Senate also has the important power of confirming presidential appointees, such as federal judges and ambassadors. It's also the body that confirms the president's pick for Supreme Court justices. 

That power is of particular importance this election year. Justice Antonin Scalia died unexpectedly in February. He was a conservative appointed by President Ronald Reagan. President Barack Obama named Merrick Garland as his replacement, but the Republican-controlled Senate has refused to hold confirmation hearings because they are holding out for a Republican to win the presidential election and pick their own justice. If Clinton wins the White House but Democrats don't win the Senate, it will be difficult for her to fill the vacancy.  

What are the Senate races to watch?

North Carolina:  The incumbent, Republican Richard Burr, should have been safe but is facing a competitive race from Democrat Deborah Ross, who is a former state representative and head of North Carolina's American Civil Liberties Union chapter. The fight over the so-called "bathroom bill," which requires people to use the bathroom that corresponds to the gender on their birth certificate, has been a major issue in the campaign.

Pennsylvania: Republican Patrick Toomey is trying to fend off Katie McGinty and hold onto his seat. Like other Republicans up for re-election, Toomey has struggled with whether to endorse Trump. So far, he hasn't. McGinty has dubbed him "Fraidy-Pat," while he calls her "Shady Katie."

New Hampshire: In one of the fiercest races in the country, Republican Kelly Ayotte is defending her seat against the state governor, Maggie Hassan. Ayotte has fumbled over her association with Trump. In one debate, she said he would be a good role model for children — then afterward issued a statement ditching that position.

Missouri: Republican Roy Blunt, a congressman for nearly 20 years, should have easily cruised to re-election. But then 35-year-old Jason Kander, Missouri's current secretary of state, came along. He made it a surprisingly tough race and forced Blunt to up his game.

Indiana: This is an open seat due to a retiring Republican senator. Former governor and Democrat Evan Bayh used to hold the seat, but didn't run for re-election in 2010 — he's now trying to get it back. Republican Todd Young is trying to prevent his return to the chamber.

Nevada: Senate Minority Leader Harry Reid is giving up this seat and Democrat Catherine Cortez Masto would like to take it over. But she's facing competition from Republican Joe Heck, currently a member of the House of Representatives.

Governor races

Also on Nov. 8, Americans in 12 states will be voting for their next governor: Delaware, Indiana, Missouri, Montana, New Hampshire, North Carolina, North Dakota, Oregon, Utah, Vermont, Washington and West Virginia.

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Five governors are running for re-election, the rest are open races. Initially Indiana's incumbent governor was seeking re-election, but Mike Pence withdrew from the race to serve as Trump's running mate.

Ballot measures

Voters in 35 states will be weighing in on various policy proposals with a "yes" or "no" vote. Some ballot measures are deep in the weeds, tweaking state laws here and there. But others relate to more major issues like taxes, education, raising the minimum wage and legalizing marijuana.

Some are more unusual, like in California, where there is a proposal to require actors in adult films to use condoms. Voters there will also decide whether to ban plastic bags.

Local and state elections

Residents in 25 cities will be voting for mayor on Nov. 8, including Baltimore, which experienced violence and unrest last year when Freddie Gray died after being arrested and suffering an injury while in police custody.

Municipalities across the U.S. are also electing city council members.

There are also elections in state legislatures. According to a calculation by Ballotpedia, 80 per cent of the country's legislative seats are up for election.

Americans will also vote for school board members and will elect judges, both at their local and state levels.