CROW AGENCY, Mont. — The young woman quickly set down the decorations she was mounting on her parade float.

“That’s Tester?” she exclaimed.

She pulled out her phone and ran over to get a picture with the two-term Democratic senator who was greeting parade participants at the 100th annual Crow Fair here last month.

But it wasn’t just Tester who showed up at the multiday festival on the Crow Reservation that’s known as the teepee capital of the world. Over the course of two days, the state’s Democratic and Republican candidates for Senate and House all stopped here. It’s one of those events Montana politicians just don’t miss.

Native Americans make up about 7 percent of the voting-age population in Montana, and have been a crucial constituency for Tester, who’s won his two previous Senate elections with less than 50 percent of the vote. He’s in another competitive race this year in a state that overwhelmingly backed President Donald Trump in 2016.

In neighboring North Dakota, where Democratic Sen. Heidi Heitkamp also faces a tight race, native Americans are 5 percent of the voting-age population. Democrats have to hold on to both seats if they’re to have any shot of winning the Senate. And in Arizona, which is one of the party’s best Senate pickup opportunities, Native Americans are nearly 6 percent of the voting-age population.

Besides it being a historic year for Native American candidates — with the House likely to welcome at least one Native American woman next year, a first — Native American voters could help decide some of this year’s most competitive races.

Watch: In Montana, Searching for Votes in the ‘Teepee Capital of the World’

Big Sky Country

With a driving rain dampening activity at Crow Fair, the master of ceremonies pulled out a microphone.

“Vote for Kathleen Williams for Congress. Your vote counts,” Willie Stewart’s voice boomed throughout the maze of teepees at Crow Agency. The grounds lie just across what’s now Interstate 90 from where Native Americans defeated U.S. forces at the Battle of Little Bighorn.

Stewart had been speaking with former state Rep. Kathleen Williams, the Democratic nominee for Montana’s at-large House seat. The Native American vote in Montana is just as important for House Democratic candidates, who also run statewide.

“A Democrat cannot win Montana without the Native vote. You just can’t,” a Democrat familiar with the state said. 

Williams is challenging GOP Rep. Greg Gianforte, who won a special election last year with the backing of the Crow Tribe’s administration. Crow tends to be more conservative than other reservations because of mining. (The Absaloka Mine generates revenue for the tribe.)

“There is a lot of coal on the Crow reservation, and we’re not here to say you should develop it, but the federal government shouldn’t stand in the way if the tribe wants to develop it,” Gianforte said in an interview at Crow Fair. 

He acknowledged, though, that the reservations in Montana have typically backed Democrats. Crow, for example, has a complex political history. In 2008, the tribe adopted Sen. Barack Obama after he became the first American presidential candidate to visit the reservation.

“It’s incredibly important just to show up. That’s why I come to these things,” Gianforte said.

At the conclusion of the grand entry powwow, during which Gianforte and Williams marched together, both were asked to address the crowd. The volume of applause after each candidate’s remarks suggests the tribe may be with Williams this year.

But for Williams and Tester, that support is contingent on organization and turnout.

Native American voters often turn out in higher rates for tribal elections than they do for nontribal ones, according to the National Congress of American Indians, a nonprofit organization that represents tribal governments and citizens. And only 66 percent of voting-age Native Americans were actually registered to vote, according to 2012 Demos data cited by the NCAI.

The Tester campaign has a full-time staffer dedicated to Native American issues, and the state Democratic Party has two Native American organizers at each of the seven federally recognized reservations in the state.

“I’ve always voted Democrat,” said 62-year-old Crow resident Curtis Brien, who approached Tester before the parade to express his concern about Trump. “He’s a scary man,” Brien said of the president.

As the former chairman of the Senate Indian Affairs Committee, Tester’s built up credibility on the reservations.

His Republican opponent, state auditor Matt Rosendale, stopped at Crow Fair the day before Tester but did not stay for the grand entry with the other federal candidates.

“It’s part of our population, so any part of our population is important,” Rosendale said when asked about the importance of the Native American constituency in the state.

Other races

The Native American vote could make a difference this year in several competitive races.

Arizona is home to one of five Senate races rated a Toss-up by Inside Elections with Nathan L. Gonzales. The largest Native American population in a House district that’s not rated safe for either party is in the state’s 1st District. Native Americans make up nearly 23 percent of the voting-age population in the 1st, where Republicans are trying to unseat freshman Democratic Rep. Tom O’Halleran. Inside Elections rates the race Leans Democratic.

In a Democratic takeover opportunity, in New Mexico’s 2nd District, Native Americans are nearly 6 percent of the voting-age population. Inside Elections rates the race Leans Republican.

In a handful of other competitive races — from California’s 50th District to Minnesota’s 8th District — Native Americans represent at least 3 percent of the voting-age population.

But it’ll be up to candidates — on both sides — to turn those voting-age residents into voters.