Clinton and Trump, shown here at the third and final presidential debate in Las Vegas, Nevada on Oct. 19, 2016, need the support of swing states to win the election. Reuters

After months of ceaseless campaigning and round-the-clock visits to every state by both candidates, the fate of the presidency ultimately lies in the hands of the swing states. Referred to as battleground states or purple states, these districts have comparable support for both parties, making their outcome nearly impossible to predict.

Many states are solidly Democratic or Republican and have voted for the same party election after election. Forty states have voted for the same party since 2000, according to Politico. Thirty of those states have voted for the same party in the past five elections.

This year, Colorado, Florida, Iowa, Michigan, Nevada, New Hampshire, North Carolina, Ohio, Pennsylvania, Virginia and Wisconsin hold the key to the Oval Office and Trump and Clinton are in fierce competition for their votes. The future president needs 270 Electoral College votes to win. These states hold 146 of them.

Swing states have certain defining qualities that split support amongst voters evenly, making voting outcomes unpredictable. Battleground states are typically diverse in race, age, and economics. Florida, Colorado and Nevada all have a large population of Hispanic voters that can swing support in one way or another. In 2012, black voters in Virginia swung the state for President Barack Obama. Economic diversity splits many battleground states into manufacturing, agricultural and corporate divisions, splintering the vote. Crucially, swing states all have similar levels of party affiliation, dividing the vote down the middle. In Florida, both parties claim an even number of voters at 43 percent each, allowing the state to be heavily affected by independent and non-affiliated voters.

After the FBI announced it would reexamine more private emails related to Clinton Sunday, both Clinton and Trump doubled down on campaigning in swing states, using the last week of the race to visit battleground areas. Trump’s campaign has zeroed in on claiming Democratic voters, while Clinton has focused her attentions on her own party to ensure high voter turnout.

Both Clinton and Trump have set their sights on Florida as recent polls showed the gap between the two candidates narrowing. Clinton held rallies in Florida Tuesday, speaking to crowds in Fort Lauderdale, Dade City and Sanford. Trump headed to the Sunshine State Wednesday for rallies in Miami, Orlando and Pensacola.

Polls have narrowed in other swing states as well, though many show differing and conflicting numbers. A RealClearPolitics average poll had Trump up 1.4 points in Iowa, while the latest Quinnipiac poll had both candidates tied. In Nevada, RealClearPolitics showed Trump up half a point, whereas FiveThirtyEight gave Clinton a 56 percent chance of winning the state.