On November 4, 2014, Americans — well, a fraction of them, at least — will go to the polls to vote in the midterm election. As of now, polls - and the forecasts based on those polls — overwhelmingly predict that Republicans will win the Senate and make gains in the House:

This will happen even though Republicans are less popular than Democrats in national polls.

How can Republicans be less popular than Democrats yet headed for a landslide? And is the public right to be so uninterested in this campaign?

Here's what you need to know about the 2014 election.

1) Midterm elections favor Republicans

The simple backdrop to the 2014 election is that turnout in midterm elections favors Republicans and turnout in presidential elections favors Democrats.

The Republican coalition is older and whiter than the Democratic coalition. And the people who turn out to vote in midterm elections are older and whiter than the people who turn out to vote in presidential elections. This table that Harry Enten made at FiveThirtyEight shows how the electorate changed between the 2010 and 2012 elections:

The difference is even more stark if you look at voters over the age of 65. Exit polls showed they made up 21 percent of the 2010 electorate but only 16 percent of the 2012 electorate. Seniors are the most Republican-leaning age group in the electorate.

Though these numbers give Republicans an advantage in midterm elections, they are not necessarily decisive. Democrats won both the House and Senate in the 2006 midterm election, for instance.

2) Midterm elections favor minority parties

One reason Democrats did so well in the 2006 midterm election is that there was a Republican in the White House.

"One of the perennials of American politics is that the president's party loses seats in midterm elections, especially in the House of Representatives," writes political scientist Eric McGhee. "Only three midterm elections in the last century featured a seat gain for the president's party in the House: 1934, 1998, and 2002. Of those, the largest was 9 seats in 2002."

It's called "the midterm penalty," and it suggests that the president's party can only gain seats in a midterm election under the most extraordinary of conditions: the Great Depression, a disastrous impeachment effort, and 9/11 are the only examples over the last century.

There isn't really an accepted explanation for why the electorate imposes a penalty on the president's party — though this paper runs through some theories — although no one doubts its existence.

The bottom line is that the midterm penalty is real and, in 2014, it will magnify the GOP's natural midterm advantage.

3) Barack Obama is unpopular

Elections are, as a rule, a referendum on the incumbent president. And Barack Obama is not a popular president.

In August of 1998 — shortly before Democrats unexpectedly picked up seats in the midterm election — Gallup found President Bill Clinton's approval rating was 65 percent.

In August of 2006 — shortly before Republicans partly lost both the House and the Senate — Gallup found President George W. Bush's approval rating was 42 percent.

Obama's approval rating right now, according to Gallup, is 41 percent. That's a huge problem for Democrats. No wonder the Washington Post found that "Democratic candidates are keeping their distance from" Obama.

4) Democrats have no chance of taking back the House

It is basically impossible for Democrats to win back the House until after 2020. The reasons are threefold, as Andrew Prokop has explained.

First, geography has a GOP bias. Democrats tend to live in more densely packed, urban districts. Republicans tend to live in more broadly spread-out, rural districts. That makes it easier to draw maps that efficiently disperse Republicans across many districts. Democrats cluster together in a way that leads them to "waste" a lot of votes on candidates who were going to win anyway.

Second, gerrymandering has a GOP bias. In most states, politicians get to draw congressional boundaries. This is done after every Census, so the last time it was done was after the 2010 Census — which followed the 2010 election, where Republicans swept into power in state legislatures across the country. The result was some pretty epic gerrymanders. In Ohio, for instance, Democrats won 52 percent of the House vote in 2012. But they only got four seats to the GOP's 12:

Neat, huh? You can see some of the other most gerrymandered states here.

The combination of geography carrying a GOP bias and gerrymandering carrying a GOP bias means that Democrats can't just win back the House by winning more votes.

In 2012, they won won 1.4 million more votes than Republicans, but Republicans ended up with a 234-201 majority in the chamber. To win back the House, Democrats need to win a lot more votes. They're not going to do that in a midterm election when they hold the White House.

And that gives Republicans a third advantage in the House: the power of incumbency. All else equal, incumbents have an advantage over challengers. "On average, an incumbent in 2012 ran five percentage points ahead of a non-incumbent candidate from the same party in a similar seat," John Sides and Eric McGhee of the Monkey Cage wrote. And Republicans have a lot more incumbents in the House than Democrats.

5) Republicans are very likely to win the Senate in 2014

Unlike in the House, where every seat is up for reelection, only about a third of the Senate is up for reelection in any given cycle. In 2014, the third of the Senate up for reelection is the third of the Senate that won their seats in 2008. And since 2008 was a very Democratic year, that means Democrats are caught defending many more seats than Republicans.

Of the 36 seats up for reelection in 2014, Democrats control 21 of them. Republicans only control 15. So Republicans have many more opportunities to win seats than Democrats do.

That's one reason why pretty much every major forecaster is currently projecting that Republicans will retake the Senate in 2014. The New York Times gives them a 67 percent chance. The Washington Post gives them a 61 percent chance. "The most likely outcome involves the Republicans winning about the six seats they need to take over the Senate, give or take a couple," writes Nate Silver.

6) Republicans are very likely to lose the Senate in 2016

Though Senate Democrats are in bad shape this year, they're not particularly concerned. That's because they're pretty sure that, even if they lose the Senate in 2014, they'll win it back in 2016.

The 2016 Senate map is even more favorable to Democrats than the 2014 Senate map is to Republicans. The 2016 election puts the Senate class of 2010 up for reelection. And 2010 was a very good year for Republicans — which means the 2016 election will leave Republicans defending a ton of seats.

As of now, it looks like Democrats will be defending 10 seats to the GOP's 24, and doing it amidst the more favorable demographics of a presidential election.

7) The average age on the Supreme Court is 68

Because Congress is currently gridlocked and because a GOP takeover of the Senate is likely to be reversed in 2016, it's common to see people argue that the 2014 election doesn't much matter. Silver, for instance, called it "the least important election in decades."

And it may well be! Or it could be one of the most important midterm elections in decades.

The Supreme Court is currently divided 5-4. But Ruth Bader Ginsburg is 81. Antonin Scalia and Anthony Kennedy are both 78. Stephen Breyer is 76. John Roberts could decide he wants to live his dream of being a Hollywood sound engineer before it's too late.

If Republicans take control of the Senate in 2014 then they'll have substantial veto power over any efforts President Obama might make to fill a vacancy that could reshape the Court. But if Democrats hold the Senate and Antonin Scalia unexpectedly retires, then the 2014 election might end up swinging control of one of America's three branches of government, with untold consequences that will reverberate for decades.

For that matter, today's Supreme Court is the direct result of George W. Bush's contested election. If Al Gore had won the presidency in 2000 and reelection in 2004, then William Rehnquist and Sandra Day O'Connor would likely have been replaced by Democrats, and Supreme Court jurisprudence in the years since would be very different.

The irony, of course, is that people said the 2000 election was one of the least important in history, too.

8) 36 states are holding gubernatorial elections this year

The House and Senate get most of the attention in midterm elections. But 36 states are also choosing who will be their next governor.

That matters for state politics, obviously. For most people in most states, the person sitting in the governor's chair probably matters more than who represents them in Congress. But if you're a political junkie who only cares about national elections, then you should still keep an eye on the governor's races: presidents tend to be plucked from the governor's mansion, not from the House or Senate.

Right now, Republicans hold 29 governorships to the Democrats' 21. But of the 36 seats up in 2014, Republicans are defending 23 and Democrats are defending only 13. That gives Democrats an edge, but it comes amidst the unfavorable climate of the midterm election. As such, Democrats aren't likely to make big gains.

Wikipedia has a nice round-up of predictions, but a good baseline can be found in Larry Sabato's forecast: he sees the likely range as somewhere between Democrats picking up two governorships and Republicans picking up one.

9) Local elections are really important

The biggest bias in election coverage isn't towards Republicans or Democrats or even towards conflict and sensationalism. It's towards national elections rather than local elections. This is partly a question of resources: it's a lot easier for a news organization to cover national politics than local politics. And part of it is that the media covers elections as the culmination of the bloodsport of American politics, and local elections don't really count towards that.

But insofar as elections are about making and changing the laws that affect people's lives, local (and state) elections are wildly underemphasized. The major decisions around infrastructure, education, and criminal justice policy are made at the state level. The decisions around zoning, occupational licensing, and the management of many public services are made at the local level. For most Americans, these decisions will be as or more consequential than anything the federal government does.

Moreover, turnout is so low in state and local elections, and people have so little information, that individual voters are much more powerful at the state and local level than they are at the federal level. This November, hundreds of cities will be choosing new mayors and new city councilmen — and that's to say nothing of superintendents, county executives, comptrollers, and all the rest. These elections matter, but national political parties and the national media devote a whole lot less time and resources into making people feel like they matter. So while you're obsessively tracking the national polls in September and October, take some time out to learn about who's running for what in your city.