In the first three months of her presidential campaign, Hillary Rodham Clinton has assembled a massive political battleship — hiring more than 400 staff members, collecting reams of expensive polling data and tapping top-flight consultants.

The details of her sprawling operation emerged this week in a newly filed campaign finance report. The documents showed that Clinton’s organization has spent nearly $19 million — or 40 percent of the $47 million it raised in its first quarter, a year and a half before the 2016 election.

Campaign officials said they needed to expand quickly to be able to weather a surprisingly competitive Democratic primary fight and intense general-election battle.

But the large expenditures cut against the image Clinton’s team has promoted of a lean organization that would not repeat the mistakes of what many considered her undisciplined campaign in 2008. And they raise questions about whether Clinton’s fundraising can keep pace with her rapid spending.

Clinton’s fundraising total between her mid-April announcement and June 30, the end of the quarter, reflected a much larger haul than that of any of her rivals in either party. But she will face a challenge in maintaining that pace: Two-thirds of her money from individuals came from contributors who have given the legal maximum and could not be tapped for additional donations until Clinton began fundraising for the general election.

Finance records show that the campaign spent nearly $6 million in salaries and benefits for its ballooning staff, accounting for the largest expenditure category. Along with big investments in fundraising and online advertising, the campaign spent thousands on private jets and high-end event production.

The campaign’s fast expansion speaks to the unusual pressure Clinton is under as she tries to reconcile her early dominance in the race with her team’s efforts to convey an image of hard-working frugality, often with intimate appearances rather than large-scale rallies.

“Hillary Clinton isn’t sneaking up on anybody,” said David Axelrod, a longtime adviser to President Obama. “It’s not like you can ramp up at your own pace. There are expectations of her campaign unlike anybody else’s campaign right now. Because she is expected to function like a presumptive nominee, she is expected to have an operation commensurate of that.”

Details in the newly filed reports paint a picture of a campaign harnessing the latest technological tools and constructing the kind of deep ground operation that Clinton lacked in her 2008 bid. That kind of organizing capability has gained importance as Sen. Bernie Sanders (I-Vt.), one of Clinton’s rivals for the Democratic nomination, has drawn large crowds and gained ground in polls.

“What she has to do is reach people where they live, work and pray to not only get them to commit but get them out,” said longtime Democratic strategist Donna Brazile, who managed then-Vice President Al Gore’s 2000 White House bid.

Clinton’s operation is paying rent in 25 cities across nine states, Federal Election Commission filings show. Along with about 340 staff members on the payroll, the campaign had hired nearly 60 field organizers by the end of June.

“It’s a sign that she’s approaching the campaign differently than the last time,” Axelrod said. “They didn’t have as thoughtful an approach to laying the foundation for that campaign, and it ended up hurting them when it ended up being an organizational fight.”

Clinton’s team has spent big to spur social-media buzz and build a sophisticated voter database similar to the one Obama’s 2012 reelection campaign used.

The campaign paid nearly $1.4 million for online ads to Bully Pulpit, which is run by a former Obama digital-marketing strategist. The New York firm Blue Wolf Group received more than $300,000 for technology consulting.

The team also shelled out nearly $1.5 million to three polling firms, including that of strategist Joel Benenson, a sizable investment in focus groups and message testing.

The rate of spending by the campaign, which could become a more than $1 billion operation if Clinton wins the nomination, underscores the premium her aides are putting on building a massive in-house infrastructure. That’s in contrast to many of her Republican rivals, who are outsourcing various political functions to outside allies.

Still, there are signs that Clinton will lean more heavily on outside support than Obama did. Her operation paid $275,615 to Correct the Record, a super PAC running a rapid-response operation in coordination with the campaign. The expenditure was for research, a campaign official said.

The new filings show that Clinton began laying the groundwork for her bid months before her April 12 announcement. She reported spending nearly $279,000 on expenses — including strategy consulting as well as payroll and travel — during a “testing the waters” period that dated to Jan. 12, a campaign official confirmed. Clinton covered those costs herself, donating them to the campaign as in-kind contributions.

“Hillary Clinton’s first quarter in the race was defined by early, smart investments aimed at building a strong foundation for our campaign,” spokesman Josh Schwerin said in a statement. “Those investments include essentially re-building email lists; hiring organizing staff; and key investments in our digital capabilities.”

One of the biggest expenditures was on fundraising. The records show that the campaign spent $2.5 million on direct-mail solicitations, showing its sense of urgency in expanding its donor base.

Clinton’s challenge is evident in the details of her contributors: $30.8 million came from those who gave the $2,700 maximum allowed in the primary, while just $8.1 million was from donors who gave $200 or less, according to an analysis by the nonpartisan Campaign Finance Institute.

That means 67 percent of her money came from maxed-out donors. At this point in the 2008 campaign, 61 percent of Clinton’s contributors had given the legal limit, while only 44 percent of Obama’s had done so. Obama’s reliance on a broad base of low-dollar donors proved to be a major advantage in his heated primary battle with Clinton, allowing him to return to them repeatedly for additional money as the race went on.

Clinton still has a larger proportion of low-dollar contributors than Republican contender Jeb Bush, who set a new record by raising 88 percent of his money in the last quarter from maxed-out donors. But Clinton does not come close to Sanders, who raised more than three-quarters of his money in the quarter from small donors, giving him a vast pool of supporters he can turn to repeatedly.

Party strategists said they expect Clinton’s online donor base to grow as the contours of the race become clearer.

“Her supporters don’t see Bernie Sanders or [former Maryland governor] Martin O’Malley as threats to her getting the nomination, or likewise on the other side, when they see the likes of Donald Trump leading the 16 or 17 candidates,” said Joe Trippi, who ran former Vermont governor Howard Dean’s 2004 White House campaign. “Someone will emerge and become a threat to her, but there isn’t one right now.”

Some of Clinton’s big spending has been visible in the larger and more slickly produced events she has held over the past month. A kickoff rally on New York’s Roosevelt Island was heavily staffed and had the polished feel of a White House event or a high-dollar outdoor concert.

The venue, which cost nearly $17,500 to rent, offered stunning views of the Manhattan skyline but almost nothing in the way of infrastructure. Everything — the stages and tents, cranes, a booming sound system, jumbo television screens, hundreds of “H” logo signs, pallets of bottled water and portable toilets — had to be rented or bought and hauled to the island. Spotty cellular service had to be augmented with boosters paid for by the campaign.

Anne Gearan contributed to this report.