If you hear a knock on the door these days, it might be a volunteer for Elizabeth Warren. If your phone rings, the caller could be a Bernie Sanders backer. And if you turn on the TV, it’s a near-guarantee you’ll see yet another Mike Bloomberg ad.

Those Democratic presidential campaigns have ramped up in the biggest ways in Colorado by hiring dozens of staffers combined, rallying volunteers and plotting out their ground games before the state’s March 3 primary.

Time is running short, with the start of mail voting here just a month away. Yet as the major candidates in make plans to compete in the 15 states and territories with Super Tuesday contests — including a few with larger delegate prizes, including the mother lode of California — not all are fighting to win in Colorado just yet.

So far, it has been the battle of the billionaires versus the champions of the liberal grassroots.

Denver-based political strategist Rick Ridder calls January “the scrambling period” of the primaries, as candidates polling well in Iowa, New Hampshire and other early states take a hard look at their tight resources and plot out strategies for Super Tuesday and beyond. The two candidates complicating this typical dynamic are Bloomberg and fellow billionaire activist Tom Steyer, both of them flush with their own cash and eager to compete in many second-wave states, including Colorado.

The leading moderate candidates for the Democratic nomination in national polls — former Vice President Joe Biden and former South Bend, Ind., Mayor Pete Buttigieg — still have a lot of work to do in Colorado.

Biden has just started building his operation, announcing a Colorado state director in the last week. And Buttigieg’s local activity so far has been coordinated entirely by volunteers, though the candidate visited Denver on Wednesday night for a grassroots fundraiser that drew eager supporters.

As for the lower-polling candidates in the still-crowded field of 12 — including U.S. Sen. Michael Bennet of Colorado, whose national headquarters is in Lakewood — most are fighting just to survive the first contests.

Colorado’s value varies for candidates

Ridder and other political experts say Colorado will matter in the race to determine who takes on President Donald Trump in November. It’s just a question of how much, and to which candidates.

Of Colorado’s 79 delegates, 67 “pledged” spots will be apportioned based on the results of the March 3 primary. That same day, five states offer larger bounties, including 416 up for grabs in California, 228 in Texas and 110 in North Carolina.

Colorado offers a less diverse electorate than some states, but its high numbers of Latinos and college graduates are likely draws for some candidates.

Here’s where it gets more complex: In the Democrats’ all-proportional system, any candidate who finishes above 15% in a congressional district or statewide will earn delegates, giving each state some importance. But it’s up to candidates to decide whether to build large staff operations, splurge on targeted TV and digital ads without much of a local presence, or rely on momentum out of early contests to hurriedly shift resources to new states.

“This is a delegate race, and no matter what everybody says, fundamentally your goal is to get 50% plus one of the delegates at the Democratic National Convention,” said Ridder, who’s not working for any campaign. “So you’re beginning to organize in Super Tuesday states. … You might not think you will win Colorado, but you damn well better make sure you get 15% in certain congressional districts in order to maximize your delegate count.”

Building out a wide-scale operation to maximize delegates is exactly what Warren and Sanders, both U.S. senators who are fighting for the Democratic Party’s liberal base, aim to do in Colorado. They were ahead of the field here, establishing beachheads last year by hiring state directors, organizing volunteers and opening offices.

But in the six weeks since the more moderate Bloomberg jumped in the race in late November — with a novel plan to focus on Super Tuesday states and skip the earlier contests — the self-funded former mayor of New York City has more than caught up in terms of staffing, though he lags badly in volunteer recruitment.

Bloomberg’s big gambit

Bloomberg, who is establishing a national primary campaign that dwarfs all others, has a reported 21 paid staffers on the ground in Colorado — the largest local paid staff by far — and another dozen or so in the hiring process. The campaign plans to open at least one office in each of the state’s seven congressional districts. He has also spent more than $2 million on TV ads in the Denver and Colorado Springs markets.

“The Bloomberg campaign is building a robust operation in Colorado because of its significance not only in the Democratic primary, but also the general election,” said Ray Rivera, a senior adviser who is among the many Colorado politicos snapped up by the campaign. They also include Ridder’s daughter, Jenn, a well-regarded strategist in her own right, who has joined Bloomberg’s national staff.

Meanwhile, Steyer, a former hedge fund manager from Northern California who’s stuck in the low-single digits in the polls nationally but has been gaining in a couple early states, has begun focusing on Colorado too. His campaign expects to have as many as 10 paid employees here by month’s end, a spokesperson says, and his ads have started hitting the air.

But staffing numbers and field offices only tell you so much, say Ridder and Ken Bickers, the interim chair of the political science department at the University of Colorado Boulder.

“There’s more to it than just the inputs. There’s also enthusiasm,” Bickers said. “Bloomberg’s got tons of money. I’m not sure where his enthusiasm comes from — unless he can (pull away) the electability rationale that Biden is clinging to.”

Warren’s paid staff stands at more than a dozen, with three Front Range offices open as of last week. The campaign’s growing list of volunteers goes back to her appearances in Denver and Aurora last spring.

“When you listen to Warren, you realize that she’s very personable,” said Ken DeBecker, a Denver resident inspired to join a regular Warren canvassing group, giving him the chance to discuss the candidate’s plans for health care, Wall Street regulation and other issues on doorsteps. “And personally, I think she’s very electable because she can communicate to the average Joe and Jane.”

Sanders’ leaner operation has just a state director and a field director so far. But the Vermont senator — who beat Hillary Clinton in Colorado’s caucuses in 2016 by nearly 19 percentage points — had a ready reserve of thousands of enthusiastic volunteers to tap, both for donations and action, and he drew thousands to Civic Center in September.

Gary Ashley, a software developer in Fort Collins who voted for Sanders four years ago, has stepped up as a volunteer this time. He has hosted seven events so far, including neighborhood canvassing, a debate watch party, and phone banking to press the case for Bernie to other Coloradans and early-state voters.

“I’ve got a little granddaughter in the first grade, and they’re doing active shooter drills (at school),” Ashley said, and he likes Sanders’ proposals to address gun violence and reduce the influence of money in politics. “That’s got me activated and wanting to do something about it. Bernie Sanders seems like he cares about normal people and wants to do something about corruption.”

Primary will boost participation

Sanders’ state director, Pilar Chapa, knows the game is different this time than in 2016.

The caucuses that the hyper-organized Sanders forces won then drew about 124,000 Democratic voters to 3,010 precinct meetings. This time, after Colorado’s switch to a mail-ballot primary and new rules that allow unaffiliated voters to take part in the party primary of their choosing, observers expect participation to be several times higher — possibly exceeding 1 million — and more moderate overall.

Chapa says it’s “better to have more Coloradans engaged in the selection process,” but political experts say the need to reach more voters brings an extra challenge that even a committed corps of volunteers can’t meet. Advertising, mailers and other means of mass-messaging gain importance.

“Yeah, organization counts — but not like in a caucus situation,” Ridder said.

That leaves an opening for Biden and Buttigieg — and any other candidate still competitive after Iowa and New Hampshire vote in early February — to swoop into Colorado with paid ads and events as Colorado voters return their ballots.

It also potentially plays into Bloomberg’s flood-the-zone strategy, though there’s been no recent public polling in Colorado to gauge whether he’s building substantial support. A poll in August had Sanders, Warren and Biden leading the field here.

“We’re a smaller state on the biggest day in a contest that has unprecedented things going on,” said Bickers, the CU professor. “So I’m not going to make any predictions, other than it’s going be fun to watch how this plays out.”