Cindy Hyde-Smith’s victory in last week’s runoff election in Mississippi marked the first time voters elected a woman to Congress in the state’s 201-year history. And the win by the Republican, who was first appointed to the seat in April, officially brought the number of women who will serve in the United States Senate in 2019 to a record-breaking 24.

But the results also represent another milestone for women in politics: the U.S. now only has one state that has never elected a woman to the U.S. House or Senate.

So which state still holds that depressing designation in 2018? The answer — Vermont — might on first glance seem like a surprise.

The Green Mountain state is reliably blue and viewed as progressive — characteristics that often go hand-in-hand with gains for women in politics. It was the first state called for Barack Obama in 2008 and 2012 and is home to Sen. Bernie Sanders, an independent democratic socialist.

This year, it made headlines and history by nominating a transgender woman as governor for the first time. Vermont consistently ranks among the top states for gender parity in state legislatures, according to the Center for American Women and Politics, and was ahead of the curve when it comes to electing a woman as the state’s top executive. Voters shattered that glass ceiling back in 1984, picking Democrat Madeleine Kunin for governor (it’s worth noting that the state hasn’t elected a woman to the role since).

So what’s the deal?

First, as one of the country’s least populous places, Vermont is one of seven states with just one at-large representative in the U.S. House. That means each election cycle, residents of the state only have one or two chances to send a woman to Washington, depending on whether one of its two U.S. Senate seats is also up for a vote that year. California, by contrast, has 53 U.S. House Districts in addition to its two senators, meaning residents there have many more opportunities to elect a woman to Congress each cycle.

But beyond that, the barrier is one that has long thwarted attempts to increase the number of women in office: the power of incumbency. All three members of Vermont’s congressional delegation — Sanders, Sen. Patrick Leahy and Rep. Peter Welch — have been serving in federal office for a decade or longer. Leahy, whose tenure has earned him the title “Dean” of the Senate, has held the seat since 1975. It’s been more than 10 years since there’s been an open seat or a serious challenge.

“We have three incumbents who are popular and who have done a great job for our state and work well for the interest of Vermont and work well together and they keep running and we keep electing them,” Ruth Hardy, an incoming Democratic state senator who recruits and trains women for office as executive director of Emerge Vermont, says. “We’re really fortunate to have them as our congressional delegation, [but] at the same time it creates a bottleneck for people trying to advance in politics in the state, especially women.”

That’s not to say there aren’t benefits from incumbency. Seniority in Washington can be helpful for a small state like Vermont, especially in the Senate. But Hardy also believes the state would benefit from fresh perspectives and representation. In addition to being longtime incumbents, all three men representing Vermont are white and over 70.

“There’s a lot to be gained by having a more diverse delegation that can bring new voices to the table, so I’m hoping we can see new voices soon,” she says.

Vermont isn’t the only place where incumbency delays or derails efforts to bring more gender balance to office.

Open seats, redistricting and other shifts that render seats more competitive translates to “more ability to see gains” for women in politics, according to Kelly Dittmar, an assistant professor at Rutgers University and CAWP scholar. The 1992 election, when women ran and won in record numbers, was the first major test after districts were redrawn that decade. And this year, a “high number of open and competitive seats … helped women and political newcomers win seats,” Dittmar adds.

Given the incumbency advantage, especially in so-called “safe” seats, the barrier can be hard to overcome. And when long-held seats do open up, there’s often a crowded field of candidates ready to run. Given those realities, “being sure that women are recruited and supported to take advantage of electoral opportunities” when they do open up is essential, Dittmar says.

“That means building a bench of women candidates and pushing through party systems that too often look first to men to be sure that women are tapped when opportunities arise,” Dittmar, co-author of “A Seat at the Table: Congresswomen’s Perspectives on Why Their Representation Matters,” says.

Another route is working to create an environment where “women feel empowered to challenge those in power instead of waiting their turn, as we saw with women like [Massachusetts Rep.-elect Ayanna] Pressley and [New York Rep.-elect Alexandria] Ocasio-Cortez this cycle.”

Hardy and her peers at Emerge Vermont are following that playbook. Since its founding five years ago, the group has trained nearly 90 women to run. About 40 percent of those alumnae are currently serving in office, with more than a dozen holding seats in the state legislature. Those figures, along with the enthusiasm she hears from her fellow female politicians, give Hardy confidence that the state is poised to send a woman to Congress in the years ahead.

“When an opening happens, we’ll have a lot of women who will step up and be ready to run for Congress. It’s just a matter of having the opportunity to do so,” Hardy said. “I’m optimistic — we’re going to break through that barrier soon.”

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