2018 U.S. midterms: A primer on why November's elections matter

Here's how the U.S. midterm elections work, and how they'll reshape the American political landscape ahead of the next presidential election in 2020.

This fall, Americans choose who controls Congress for the next 2 years

U.S. President Donald Trump won't be on the ballot for the Nov. 6 midterm elections. But the outcome of the votes will likely affect how he governs. (Jim Lo Scalzo/Associated Press)

It's a referendum on U.S. President Donald Trump. It's a chance for Democrats to steer the legislative agenda. It's a test for Republicans wondering if they should embolden their actions and themselves.

Any way you slice it, the U.S. midterm elections will allow voters to significantly change the makeup of Congress about halfway through Trump's four-year term. The outcomes could reshape the American political landscape ahead of the next general election in 2020.

Here's how the midterm elections work.

When will the midterms happen?

The midterm elections will mostly take place on Nov. 6.

They are national elections, sometimes described as "off-year" elections. The Founding Fathers of the United States set up a political system of checks involving frequent, rolling American elections in even-numbered years.

House members serve two-year terms, so they run in both "on years" with presidential contests, as well as in off years, without a presidential race, along with one-third of the Senate.

The way elections are staggered means that an election — either a presidential or a midterm — ends up being held every two years.

Why so often? Because "the founders didn't want politicians to get too comfortable," explained Mark Harkins, a Capitol Hill veteran and senior fellow at Georgetown University's Government Affairs Institute.

The idea is that holding frequent elections reins in potential "unbridled ambitions," he said.

Who's actually on the ballot?

Not the president.

The full 435-seat House of Representatives will be in contention at one time because its members serve a two-year term.

Trump addresses a joint session of Congress in this February 2017 file photo. As the saying goes: 'The party that controls the chamber, controls the agenda.' (J. Scott Applewhite/Associated Press)

The Senate, which has 100 members, works differently. It's on its own cycle because senators serve six-year terms, so only one-third of Senate seats will be up for grabs every two years. This year, 35 Senate seats are in play: 33 senators, plus two special elections.

Aside from Congress, there are 39 state and territorial governorships up for grabs.

Why is the Senate on a different cycle?

Unlike the House, the Senate never stands for election at one time.

The Framers of the Constitution purposely designed the Senate "to be more politically insulated," explains Linda Fowler, a professor of government with Dartmouth College.

Are the midterms good for presidents?

Historically, no. It's quite the opposite — a fact that Trump is well aware of at a time when he's unpopular in the polls.

"When you win the presidency, for some reason, you always end up losing the House," Trump said in May at a rally in Nashville.

Trump has also expressed confidence he'll reverse the trend. How many seats in Congress his party wins or loses in the midterms will be a sign of how the populace feels about his and his party's performance.

"Presidents tend to overreach in the first two years, and midterms are a way for the populace to lodge their concerns with the chief executive," Harkins said. "Trump's not on the ballot, so the way they lodge concerns is in the House of Representatives."

In 2010, two years into his first term, Barack Obama's Democrats lost a whopping 63 seats in the House, with the then-president memorably conceding it was a "shellacking."

Bottom line: The party that has control of the White House typically loses seats.

Isn't that good for the Democrats?

If historical trends play out again this year, then yes.

Consider that in nearly every midterm election after the Second World War, from 1946 to 2014, the party occupying the White House ended up suffering net losses of House seats. (The only exceptions were in 1998, when Bill Clinton picked up five Democratic seats, and in 2002, when George W. Bush picked up two seats for his Republicans.)

Construction crews work to replace a section of the old U.S.-Mexico border wall near Tijuana on June 28, 2018. (Jorge Dunes/Reuters)

"Generally speaking, if you're a fan of Republicans and Trump, you'll be nervous," Harkins said. That's because the average net loss for incumbent presidents after the Second World War was 25 House seats and four Senate seats.

By July, Republicans had a 236-193 seat majority over the Democrats, with six vacancies. In August, Ohio Republican Rep. Troy Balderson was declared the winner of a special election after weeks of recounts. He is expected to be sworn in the first week of September, raising the Republican edge to 237-193, with five vacancies.

The number of "pickups" needed for the Democrats to win a majority in the House this year varies depending on whether vacancies are factored in. Assuming the Democrats hold all of their current seats, the most commonly cited number of Republican seats they'd need to flip is 23.

The progressive political group Swing Left, for example, bases its math on which party controls each seat given the most recent election results. It assumes all 435 seats will be filled by the midterms.

That puts their count at 240 Republican seats to 195 Democratic seats, meaning Democrats need 23 Republican-held seats to win the magic number of 218 — the amount needed to take control in a full House of Representatives.

Will the Democrats take the Senate?

Republicans have an even slimmer majority in the Senate (51-49), but the Senate changing hands is a long shot.

Of the 35 Senate seats up for grabs, just nine are held by Republicans. Democrats have nearly three times the number of seats considered to be must-win, as 26 seats are currently held by senators who caucus with the Democrats.

Another challenge for the party: 10 of the Democratic or left-leaning independents running will be competing in states that Trump carried in the presidential election.

Not only do Democrats have to defend all their Senate seats, they'll also have to pick up two more by flipping Republican seats to take control. 

"It would have to be a real repudiation of the sitting president for the Republicans to give up control of the Senate," Fowler said. "It's not impossible — but it's less likely."

Will the Democrats take the House?

Their odds improved over the summer.

If the Democrats only need a 23-seat flip, the historic average of a net gain of 25 would seem to indicate they're likely to take over the House of Representatives. But in the last 25 years, the House has changed hands only three times during midterm elections — in 1994, 2006 and 2010.

The party is nevertheless optimistic. There's excitement about a possible "blue wave" that could sweep them into the House and the Senate. 

"Political statisticians are putting the odds of Republicans losing control of the House at about 50-50," Fowler said in early July.

By the end of the month, Dave Wasserman, an editor of the Cook Political Report, was guessing that Democrats were 60 to 65 per cent favourites to prevail in the House.

Why care about who controls Congress?

As the saying goes: "The party that controls the chamber, controls the agenda."

Consider this year's backdrop of the Russia investigations, legislative battles over immigration, gun rights and health care. If the Republicans maintain control, expect reinvigorated efforts to dismantle the Affordable Care Act and another swing at trying to get Trump's border wall constructed.

"They may try to find additional tax cuts, to find ways to roll back the regulatory authority of certain agencies using the legislative process instead of the president's executive authority," Harkins said.

Trump and Prime Minister Justin Trudeau have clashed recently over NAFTA negotiations and U.S.-imposed tariffs on Canadian steel and aluminum. (Evan Vucci/Associated Press)

A Democratic takeover might lead to re-examination of immigration reform, particularly as it pertains to legalizing people who were once protected by the Deferred Action for Childhood Arrivals (DACA) policy, an Obama-era program that shielded from deportation some who came to the U.S. illegally with their parents when they were young children.

While Trump could veto a DACA bill, it might cost him votes among moderate Republicans in the important battleground state of Florida in 2020.

The threat of impeaching Trump could also rise with Democrats in control of the House, as impeachment comes down to a majority vote in the House before being forwarded onto the Senate.

Does Canada have a stake in this?

Of course. Take, for example, how Canada was hit with steep tariffs on steel and aluminum.

Trump justified the move on "national security" grounds, so Republican Sen. Bob Corker, a vocal Trump critic, tried to introduce a bipartisan bill to force the president to get congressional approval to enact tariffs on the basis of national security. He was unsuccessful.

All 435 House seats are up for grabs in the midterms, along with 35 Senate seats and 39 state and territorial governorships. (Pablo Martinez Monsivais/Associated Press)

Corker accused Republican leadership of being too afraid to "poke the bear" that is Trump right before the midterms.

If the configuration of Congress changes, one might imagine that the bill would stand a better chance of advancing. Economists would see that as good news for Canada.

Does turnout matter?

Yes. Democrats are worried about a "midterm falloff."

Turnout for the midterms in the U.S. is always much lower than in general elections; it was around 36 per cent of registered voters in 2014.

Registered voters who tend to drop off at the midterms tend to be: lower-income, minorities, less educated, younger, or female. That has traditionally been a problem for the Democratic Party, as older, white voters who give a boost to the Republicans continue to participate in midterm elections in stronger numbers.

Democrats are hoping their female and millennial supporters will be motivated by anger over the Trump administration's actions to contribute to a surge in support at the polls.

What about the Russia probe?

If the Democrats took the House and the Senate, they'd have the instruments of investigatory power smack-dab in the middle of an ongoing probe into Russian meddling in the 2016 presidential election.

"As part of agenda control, investigations are determined by the parties that control the chambers," Fowler said. "But if the Republicans lose one or both chambers, those investigations will become much more aggressive — because it will be Democrats looking to damage President Trump before the 2020 presidential election."

Congressional investigations are serious and each chamber would, by law, have subpoena powers.

"They could, for example, subpoena President Trump's income-tax returns," Fowler said. "I don't think this president fully appreciates how miserable his life could become if his party loses both chambers."

With files from Lyndsay Duncombe

About the Author

Matt Kwong


Matt Kwong is a Washington-based correspondent for CBC News. He previously reported for CBC News as an online journalist in New York and Toronto. You can follow him on Twitter at: @matt_kwong


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