A Democratic presidential candidate has not won a majority of votes in Nebraska for more than 50 years. But on Thursday, Hillary Clinton’s campaign announced it would begin spending precious advertising dollars in the state. The advertising buy is focused on Nebraska’s second congressional district, and includes two ads about Clinton’s advocacy for children.

It is an expensive bet on a state that has almost always voted red. But there’s a simple reason behind what seems like a gamble: Nebraska allocates its electoral college votes not in the usual winner-take-all method, but by congressional district. So a Republican candidate can win in the state, but a Democratic candidate can still pick up electoral votes by winning over a district.

The second congressional district, which is centered in Omaha and its suburbs, has a history of occasionally voting differently from the rest of deep-red Nebraska.

The district went for Mitt Romney in 2012 but for then-Sen. Barack Obama in 2008. In 2014, when Democrats lost a wave of congressional races across the country, Democrat Brad Ashford won the district’s seat in U.S. Congress. And as a Clinton aide pointed out, the African-American share of the vote in the district is higher than the statewide average—and Clinton has shown she consistently over-performs among black voters.

The electoral college’s winner-take-all system means that reliably Democratic states like Massachusetts and Oregon—or reliably Republican states like Texas and Alabama—are never seriously contested by presidential candidates. They predictably vote Democratic or Republican. But in Nebraska and Maine—the two states that allocate their electoral votes by congressional district—there is more room for the parties to maneuver. They can spend ad dollars and campaign in states that they could never win outright.

It’s an electoral strategy that Donald Trump is hoping to take advantage of, too. This week he campaigned in Maine, which also allocates its electoral votes by congressional district but usually supports a Democrat. He held a rally in Bangor in the state’s second congressional district, which is predominantly white and rural.

Clinton has begun a broad and expensive advertising campaign in the swing states that you’d expect: Florida, Ohio, Colorado, Iowa, Nevda, New Hampshire, Virginia, North Carolina. In those states, as well as in her Nebraska ad buy, Clinton has aired advertisements that tout her role in the creation of the Children’s Health Insurance Program in the 1990s.

These are the two ads that will be playing in Nebraska.

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