By Kurtis Lee, Los Angeles Times

AURORA, Colo. — The seventh-floor suite of an isolated business tower in this area of richly ethnic enclaves bustled for much of the last year with Republican volunteers poring over voter phone lists, then dialing to speak with residents not just in English, but also in Spanish and Korean.

For the state Republican Party, which four years ago did not have a field office in this Denver suburb rife with Democratic and unaffiliated voters, the plan was simple: Begin a conversation with groups that don’t often cast ballots in midterm elections and have never had much contact with the party.

And the party has no plans of packing up and moving out.

Both major parties, along with a host of outside groups, are now gearing up for 2016, when this swing state will be back in the spotlight with a presidential race at the top of the ticket, and another U.S. Senate contest on the ballot as well.

“We’re not going anywhere,” Ryan Call, the state’s Republican chairman, said in a recent interview. “We’ll keep a substantial presence here in Aurora and around the state. But specifically here in Aurora — if this party wants to excel in elections and be relevant in 2016, we need to forge relationships with growing numbers of Hispanic and Asian-American voters — that’s what we’re prepared to do.”

With Republican Cory Gardner taking over a U.S. Senate seat as Democratic Gov. John Hickenlooper won re-election, each side in Colorado’s narrowly divided politics was claiming some successes from the tens of millions of dollars they poured into the state, a large portion of it in ground-level get-out-the-vote efforts for the state’s first mail-only election.

In Colorado, where each voter was mailed a ballot in mid-October, early outreach was crucial.

Americans for Prosperity-Colorado, an arm of the national conservative nonprofit bankrolled by the billionaire Koch brothers, has had, since January, almost three dozen paid field staff in the state and hundreds of activists knocking on doors and making phone calls. In 2012, the group had five paid staffers, said state director Dustin Zvonek.

“Our plan is to continue to build our grass-roots infrastructure each and every year to continue to engage in policy fights at all levels of government,” Zvonek said. “A lot of attention is given to the TV ads we run or the direct mail, but our real strength is our grass-roots infrastructure — our ability to have conversations with Coloradans on the phone or at their doorsteps.”

Because Americans for Prosperity is considered a social welfare nonprofit, it does not have to disclose its donors. However, public TV ad buys show the group spent about $2 million in ads this year targeted at Democratic Sen. Mark Udall’s support of the Affordable Care Act. It spent about $365,000 in express advocacy such as campaign literature and voter outreach — which specifically targeted Udall and are required to be made public under federal election law.

Zvonek says the conservative group plans to hire additional paid staffers in the months ahead.

“We’re talking to people at their doorsteps. It’s an investment and a connection that will help give us leverage,” Zvonek said, noting the state’s growing number of unaffiliated voters who can break either way.

But conservatives are not the only ones poised to maintain a presence here in a state that twice voted to elect Barack Obama as president.

In an ambitious ground operation of its own, the Democratic Senatorial Campaign Committee this year invested $60 million in its so-called Bannock Street Project, named after the street where Colorado Sen. Michael Bennet, the group’s chairman, housed his campaign headquarters in 2010.

That year, as the GOP saw sweeping victories nationwide, Bennet defeated Republican Ken Buck by 2 percentage points in part because of a robust field team. That team tripled in size for 2014, according to Paul Dunn, national field director for the DSCC.

While the Democratic Senate candidate lost, senior DSCC aides point to some underlying success: Their analysis of incomplete returns shows the electorate in Colorado was about 1.5 percentage points more Democratic than in 2010, with more 18- to 34-year-olds voting in 2014 than four years ago. Democratic volunteers knocked on 1.3 million doors in Colorado this year — a substantial increase from 2010, Dunn said. National Democratic officials said that Hickenlooper’s narrow victory would not have been possible without that effort.

“While field operations alone will never be enough to trump a national wave election like we saw in 2014, the final numbers coming out of Colorado clearly demonstrate our ability to expand the electorate and make it more Democratic and more diverse,” Dunn said in an email. “Democrats in Colorado know that we must continue to invest in these programs for us to be successful in 2016 and for years to come.”

Other Democratic-affiliated groups, such as billionaire environmentalist Tom Steyer’s NextGen Climate, spent millions on Colorado ground efforts, says its state adviser, Craig Hughes, a longtime Democratic strategist who also served as state advisor to Obama’s campaigns here. Hughes says he expects the efforts to continue into 2016, with increased targeting of “climate voters,” through mail, TV ads and volunteers on the ground.

Robert Loevy, a professor emeritus of political science at Colorado College, said that with these groups remaining in the state, an election season that seems nonstop is just that.

“The door knocking we’re seeing with campaigns is something that’s going to go on incessantly, much like it already has here in the last eight years,” Loevy said. “Before long, the ads will be back on TV and the campaign literature in the mail. It’s a normal way of life here — election after election.”

MCT Photo/Maeve Reston/Los Angeles Times

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