An image from Hillary Rodham Clinton’s presidential campaign announcement video released on Sunday. (AFP/Getty Images)

On the surface, Hillary Rodham Clinton is starting her presidential run small. She’s being driven halfway across the country in what she’s dubbed her “Scooby Doo van,” getting out at diners and gas stations to chat with people. She plans an intimate listening tour with everyday Americans, beginning Tuesday in the town of Monticello, Iowa.

Behind the scenes, however, the vast network Hillary and Bill Clinton have cultivated over four decades in politics is whirring back to life to build a behemoth ready to last far beyond the Democratic primaries. It will be the largest operation ever mustered by the Clintons, designed to compete in what is expected to be the most expensive presidential election in U.S. history.

“There’s going to be a juggernaut,” said John Morgan, a Clinton supporter and fundraiser in Florida. “This is straight to the World Series — no spring training, no regular league play, no wild card games.”

Already, an “overwhelming” amount of money has come in via the campaign Web site, according to a person familiar with the online response.

Still, the Clinton team says their mantra is: Take nothing for granted. Her campaign advisers say they anticipate a competitive Democratic nominating contest and that she will fight to earn every vote — especially here in Iowa, whose quadrennial first-in-the-nation presidential caucuses have humbled many front-runners, including Clinton in 2008.

Bill and Hillary Clinton at the Iowa State Fairgrounds rally in Des Moines in 2007. (Melina Mara/The Washington Post)

Yet most Democrats see Clinton, in the absence of a strong challenger, as their inevitable nominee. So it was that on Day One, Clinton’s campaign and its allies turned to building up an infrastructure for what promises to be a long, costly and bruising journey to the White House.

The nascent Clinton team is laboring to assemble a grass-roots political organization on the ground in all 50 states by next month, when she will formally kick off her campaign with her first rally and major speech.

Clinton’s activity and footprint will be particularly robust in Iowa, also a general election swing state. Aides said she plans to help rebuild the beleaguered Democratic Party here, including recruiting candidates to run for local offices like school board and growing a corps of volunteers to help in the general election.

Campaign officials asked governors, senators and other elected officials to not simply issue endorsements — many did so immediately — but to send e-mails and other messages that could mobilize their own volunteers and constituents behind Clinton’s candidacy. In a Sunday memo, the campaign composed suggested tweets for elected officials to send, sharing her announcement video and inviting them to sign up with her campaign.

Campaign chairman John Podesta and finance director Dennis Cheng began to activate Clinton’s donor network with e-mails Sunday, followed by calls from regional fundraisers to bundlers across the country. Each was given an individual fundraising goal.

Supporters who raise the maximum legal contribution of $2,700 for the primary from at least 10 friends in the next 30 days will be named “Hillstarters” and invited to a donor retreat next month. The $27,000 threshold is relatively low for a modern campaign, but aides said it is designed to be accessible and help expand the donor pool.

“If you started out and said, ‘Go raise us $270,000,’ for a lot of people that’s overwhelming,” said Democratic strategist Steve Elmendorf, a Clinton supporter. “But if you say, ‘In a month, raise $27,000,’ there’s obviously people who can do that. Once they do and they feel they’re part of the movement, you can ask them to do something else.”

Former President Bill Clinton and daughter Chelsea listen as his Hillary Rodham Clinton speaks at a campaign fundraiser in New York in 2007. (Keith Bedford/Reuters)

Tom Nides, who was a top deputy to Clinton at the State Department and is informally advising her campaign, said that by focusing for now on modest fundraising goals, her team was “going about it exactly right.”

“They are concentrating on building a strong grass-roots that is going to be there for the long term,” he said.

Podesta, Cheng and other top advisers held a conference call with major donors Monday afternoon, including campaign vice chair Huma Abedin, who called in from Clinton’s van shortly after stopping for lunch at a Chipotle restaurant in Ohio. Veteran bundlers said they sense a more sophisticated, buttoned-down approach to the 2016 fundraising operation than in past Clinton campaigns.

“You have to remember, they have a base, they have a lot of friends, and it’s not hard for them to get major Democratic supporters to sign up within 24 hours,” said Jack Rosen, a Clinton friend and New York real estate executive. “The big question mark is, how do you gain traction with the rest of America.”

For its part, Priorities USA Action, the pro-Clinton super PAC that struggled to get donor commitments in the absence of an official campaign, immediately ratcheted up fundraising efforts.

Top Clinton backers are being asked to write seven-figure checks to the group, according to a person familiar with the group’s plans. And the super PAC’s executive director, Buffy Wicks, was set to meet with wealthy liberal donors gathered in San Francisco for a meeting of Democracy Alliance, an organization that advises some of the party’s biggest contributors.

The campaign’s early strategy, people familiar with the outreach say, is to rely on the existing Clinton network to generate as much money for the campaign as possible without using the candidate’s time. That will free up Clinton to spend more time on retail politics, although top advisers such as Podesta will figure as her surrogates at early finance events.

The approach capitalizes on the years the Clintons have spent amassing a group of loyalists from Arkansas to California to New York. Skip Rutherford, dean of the Clinton School of Public Service at the University of Arkansas and a longtime Bill Clinton adviser in Little Rock, said the family’s Arkansas network has been abuzz.

“I never dreamed back in 1991 that this would be happening like this again,” Rutherford said. “But for young people — the sons, the daughters, the grandchildren of many who started with Bill Clinton in the 1980s — this is an electrifying moment. They feel this is not just telling old war stories, but this is a campaign about me.”

Even for major Democratic donors, who have grown jaded by rote political campaigns, Clinton’s video — striking in its focus on a diverse medley of ordinary people — struck a chord.

“I wasn’t sure what I was expecting, but after I watched it and shut it off, I smiled,” said Robert Wolf, a former president of UBS Investment Bank and an Obama friend who is backing Clinton. “It showed what our country is, which is the most diverse place in the world. It had a nice touch.”

Donors and other supporters said they are pleased to see Clinton begin in small settings, thinking that it plays to her strengths.

“If you’re Obama, you go to Springfield in a mythical setting and give an oratory that’s worthy of Lincoln,” Paul Begala, a former Clinton adviser who helps run Priorities USA Action, said about Obama’s 2007 campaign kickoff in Illinois. “If you’re Hillary, you get in a van and you go house to house, table to table. This process is the quintessential Hillary.”

For the Clinton campaign, the challenge will be corralling the hundreds of people who will want to demonstrate their value to her campaign. Already, supporters are jockeying to position themselves as the top point person for her fundraising operation in their area, according to people familiar with the dynamics.

Donors and other supporters have been especially excited that Clinton is riding in a van to Iowa, rather than on a private jet.

“They need to save that van for her presidential library,” Rutherford said, comparing it to the sunglasses Bill Clinton wore on “The Arsenio Hall Show” in 1992. “It’s one of those artifacts.”

Gold reported from San Francisco. Anne Gearan contributed to this report.