(CNN) Republican Rep. Mike Coffman is sitting in a church communicating with a group of Spanish-speaking parishioners in their native tongue with a heavy American accent.

He quietly listens to their questions, answering them slowly and methodically. The parishioners are constituents he desperately needs to vote for him if he has any chance of winning re-election in his suburban Denver seat in November.

Colorado's 6th District is the ultimate battleground. For years, Democrats have poured millions of dollars in here to try to beat Coffman, but always fall short. In 2016, Hillary Clinton won here by 9 percentage points, but Coffman still won re-election by more than 8 points.

This year, Democrats on a national level are looking to this district as a bellwether, and the party has a poster candidate for a nominee -- Jason Crow, a combat veteran. If Democrats can finally win here, strategists say, they feel confident about taking back the House.

For Republicans, the race is a test of whether an incumbent congressman who has crafted a strong personal brand in an increasingly diverse district can survive an election where the enthusiasm is clearly on the Democratic side.

So Coffman is relying on his political survival skills that have helped him win against all odds in the past. Being there for his diverse district is Coffman's calling card.

To signal a kinship with his Mexican and Salvadoran American constituents, Coffman hired a Spanish tutor, with whom he studies every Sunday for two hours. She sits with him at his event, and he turns to her when he needs a language lifeline.

The Hispanic community is just one of the large ethnic enclaves in his district, and Coffman knows it. He had just come from a visit with the Chinese community, and is next headed to an Ethiopian celebration, where he will be greeted as a rock star because of the time and effort he has spent helping combat human rights abuses in Ethiopia.

"With this President, this midterm is going to be rough for Republicans. It's those members of Congress that have established a brand in their district, that is independent of quite frankly, of the party in Washington, DC, that are going to survive this," Coffman told CNN in an interview here.

"They don't see me as a Republican, or they don't see me in a partisan way. They just see me as their congressman," Coffman said.

The Trump factor

Crow is taking every opportunity he has to tie Coffman to President Trump, whose immigration policies, chaotic approach to governing, and often crass tone has made him unpopular with key voting blocs here -- from ethnic groups to independent suburban women.

He's never run for office before, which is something he emphasizes as he goes door to door making his pitch to voters.

"I'm a first-time candidate, I've never run for anything before but I feel really strongly about the direction our country is going in," Crow tells Esperanza Valle, while standing on her front stoop.

He won't take PAC money and is running hard against everything Washington, even his own party leadership.

"From day one of this campaign, I've been very clear, this is about bringing the new generation of leadership to Washington to turn the page and to move us forward as a country. We have this culture of partisanship that has delivered dysfunction and lack of progress, right? And this applies for Democrats and Republicans, right?" Crow tells us in an interview.

"I will not vote for Nancy Pelosi," he says.

But Crow insists he will be able to beat Coffman this year -- something previous Democratic candidates failed to do in the past four elections -- for one reason: the man in the White House.

"We live in a very different world than we lived in just two years ago. Donald Trump is President of the United States," Crow said flatly.

In television ads blanketing the airwaves, Democrats paint Coffman in grainy black and white footage as a Trump puppet.

Coffman has worked hard to distance himself from Trump -- on everything from immigration policies to the President's twitter tirades.

"When they were separating families on the border, I certainly was one who protested that -- against the administration -- went down to the border to see what was occurring myself with those families, and the Administration stopped that policy," Coffman told us.

"When the President went to Europe I did statements of support, when he talked to the Europeans. Statements of opposition when he met with Putin in private."

But even so, he admitted, Trump is a big drag on his candidacy.

"There are people that are going to be swept up in a partisan lens, that probably there's not a whole lot I can say," he said.

"It's less about his policies than it is about his tone. College educated independent women, just really are offended by his tone and his mannerisms in the office. So it's baked in now." Coffman said, with resignation in his voice.

Independents are the majority here

Maybe more than any other race this year, it is all about independents in Colorado's 6th district. The district is growing so much, so fast, they now outnumber both Democrats and Republicans here.

John and Meredith Brackney were registered Republicans, but left the party after Trump was elected, and say they're not alone.

"We personally know dozens of them, well respected Republicans [who left the GOP]. They want nothing to do with that man," said John Brackney.

He was a local GOP elected official in this suburban district, has known Coffman for years and is leaning towards voting for him. But he also says it's "conceivable" that he will not.

"The only question is, is my disappointment in the President so significant that I wanna vote all the way down the ticket against Republicans," Brackney said, explaining his struggle.

His wife Meredith, who has voted for both Republicans and Democrats all of her life, is surer about her approach this year.

"I'm probably voting for the Democrat. I'm hoping for a blue wave. I think we need checks and balances, and right now we don't have any. And so, I'm planning on pretty much all Democrat," said Meredith Brackney.

Independent voter Ann Santos says she's still undecided about whether to vote Republican or Democrat in the House race here in November, but also says her vote is really going to be a protest against President Trump.

"He is so destructive, he is so divisive," Santos says of the president.

She also expresses a sentiment building for years among voters -- especially independents. She is disgusted with the chaos of Washington, and wants a change, and likes the fact that Crow has never run for office before.

"That is a plus for me. 'Cause that means that he is still wanting my vote, he is very interested in what the regular person wants. I guess yeah, I think he would be more in touch with the everyday person," Santos said.

Same goes for Dayna Kreutzer, another independent voter here who says Coffman has done a good job for the district, but thinks it's time for fresh ideas in Washington.

"I think it's time for a change. I think we're getting too set in our ways, and we need to make changes," said Kreutzer.

Battle tested

First-time candidate Crow, the Democrat, plays up his military service on the campaign trail and weaves it into his narrative.

"This is a battle for the soul of America. Two very different visions of what America is about and who we will become. I learned what the soul of America is when I served with my fellow soldiers in Iraq and Afghanistan. When I think of America, the faces of those young men and women pop into my mind," Crow told a group of supporters before they fanned out to knock on doors on his behalf.

Though Coffman doesn't talk about it as much, he, too, is a veteran. He is the only member of Congress to serve in both Iraq wars, first in the Army, then the Marines.

He says he is falling back on his Marine training for much needed stamina in this political race. He tries to do 500 pushups each day and dropped and gave us 20 for our camera.

But it's his experience on the front lines of politics -- being in a neck-and-neck race in this district several times before -- that he hopes really makes a difference.

"In a bad political environment, [we] are more likely to survive than people that suddenly find themselves in headwinds that they've never experienced before," he told us.

Coffman calls it being "battle tested."

As competitive races go, Coffman believes he is doing everything he can. Republicans in Washington say he is doing everything right.

But this year, it may not be enough -- thanks to President Trump. He says it used to drive him crazy that his own fate is so tied to Trump, whom he says he did not vote for.

Now?

"You know at this point, I'm resigned to it," Coffman said.