Republican Rep. Scott Tipton rode into Washington on a red wave that swept more than 60 House Democrats out of office in 2010. Now, with talk of a nationwide blue wave, Tipton is the one looking vulnerable.

Democrats across Colorado have been hinting for weeks that the state’s 3rd Congressional District, where their candidate, Diane Mitsch Bush, is outraising Tipton, is a “sleeper” race. On Tuesday, FiveThirtyEight, a national news organization that specializes in poll tracking, moved Tipton’s seat into its tossup category and forecast his victory by a single percentage point — in a district he won by 15 points in 2016.

After the 6th Congressional District, where Republican U.S. Rep. Mike Coffman has held on despite the demographics, the 3rd is the most competitive district in Colorado this year. Two of Colorado’s other House seats are solidly Republican and three favor Democrats.

Tipton, a Cortez native, said he isn’t taking his re-election for granted but is casting his opponent as too liberal for the sprawling 3rd District, which covers most of the Western Slope and the San Luis Valley before curving northeast into Pueblo County.

The race is more of an uphill battle for Mitsch Bush than it appears on paper. Democratic enthusiasm is palpable, but even her campaign manager says that won’t be enough to carry her across the finish line. She’s going to need to win the majority of unaffiliated voters and probably a few Republicans, too.

“Even if the blue wave hit us, there’s not enough blue in our district to make the wave meaningful,” said Mitsch Bush campaign manager Sonja Macys. “Diane needs a purple wave to win.”

The Ph.D. in sneakers

Mitsch Bush darted around her downtown Pueblo campaign office one Saturday in September wearing moss-green pants, a button-down shirt and sneakers.

The 68-year-old former Routt County commissioner and state legislator has a Ph.D. in sociology and a plainspoken way of talking. Mitsch Bush, a longtime Steamboat Springs resident, also has a belief that she’s the right candidate in the right political moment to take Colorado’s 3rd Congressional District from Tipton.

“If this were a standard job interview, Diane Mitsch Bush would be the hands-down choice against Scott Tipton for her deep knowledge of rural and Western Slope issues, and her incredible passion for her constituents,” said Ian Silverii, executive director of ProgressNow Colorado. “However, this isn’t a job interview. It’s an election in a very oddly drawn congressional district that’s stymied well-qualified Democrats in the past.”

On paper the 3rd District is less red than nearly a dozen U.S. House districts across the country where Republicans are considered vulnerable, but Tipton’s seat hasn’t attracted national money or attention — until now. What makes CD-3 different from those suburban battlegrounds where national groups have spent millions is its demographics.

It’s as big as New York State, and two of every five voters in the district live in Mesa or Pueblo counties — areas where recovery from the Great Recession is a recent phenomenon and support for President Donald Trump remains strong. Tipton outperformed the president in both counties, and he won Pueblo County, where registered Democrats outnumber Republicans, in both 2014 and 2016.

Puebloans, who are often compared to Rust Belt voters in the Midwest, told The Denver Post they believe the president’s “America first” attitude has finally brought home the economic recovery they’ve watched Front Range folks enjoy for years.

“This is sort of not new. Gary Hart never did very well in Pueblo, and he ran in the 1980s,” said Pueblo County Democratic Party chair Mary Beth Corsentino. “We still have the majority as far as registration goes here, but that doesn’t translate to Democratic votes. And that goes back to values that have been around for a long time.”

Mitsch Bush and her campaign recognize the challenge those kinds of Democrats pose for her candidacy. Pueblo County is a must-win for her.

When she received a question about Trump at The Pueblo Chieftain debate this month, Mitsch Bush didn’t mention the president’s tweets, the Russia investigation or his push for the nomination of Supreme Court Justice Brett Kavanaugh. Instead she took a local angle, slamming the president’s proposed budget because it would have cut small business loans for rural communities, farmers and ranchers.

The debate audience inside Colorado State University-Pueblo’s student center hollered when Mitsch Bush said she wanted a public option like Medicare because it’s not fair that people in Steamboat Springs pay two or three times what people in Denver do for health insurance. They shouted when she called on the federal government to invest in broadband and the electric grid.

The unaffiliated middle

Winning Pueblo County is necessary but not sufficient to carry Mitsch Bush to Washington. She will have to close a sizable gap in Mesa County, run up the numbers in small, blue pockets around resort communities, and appeal to unaffiliated voters who outnumber both registered Republicans and Democrats.

Tipton and his campaign understand that, too.

He pushed out John Salazar, the last Democrat to represent the district, in 2010 by repeating a line about how often Salazar’s vote aligned with then Speaker Nancy Pelosi’s policies. Tipton says Mitsch Bush is too liberal for the district, using her support for what he called “socialized medicine” and her wavering on the proposed natural gas pipeline from Jordan Cove to the Oregon coast as examples.

Mitsch Bush says she isn’t convinced that the project would bring enough jobs to the region to offset some of the environmental concerns, while Tipton, Gov. John Hickenlooper and both of Colorado’s senators support the project.

“According to Grand Junction’s Chamber of Commerce, we lost 6,000 residents out of Grand Junction during the last boom-and-bust cycle,” Tipton said. “They literally picked up and left. They went up to North Dakota.”

He thinks Pueblo’s steel mills could be in the running to manufacture pipelines for the Jordan Cove project even though the lines themselves will be laid in Oregon — a belief that earned him raucous applause at The Chieftain debate.

“You never take anything for granted,” Tipton said when asked about his re-election chances.

Trump’s approval rating is in the low 40s nationally and in Colorado, and midterm elections are historically referendums on the current administration. Democrats have a comfortable lead in most generic polls. The conditions are ripe for a wave election like the one that ushered Tipton into office in 2010.

Corsentino has been spotting Mitsch Bush yard signs all over town.

“We’re kind of a yard sign community,” Corsentino said. “There were Trump yard signs all over the place in 2016, and the Hillary campaign didn’t have yard signs. … I see a lot of Diane’s these days.”