NEW YORK - Democrat Hillary Clinton plans to pour half of her presidential campaign’s budget into advertising in the first three months of this year as she seeks to fend off an increasingly tough challenge from chief rival Bernie Sanders, according to a summary of her spending plans reviewed by Reuters.

U.S. Democratic presidential candidate Hillary Clinton speaks during a campaign rally at Iowa State University in Ames, Iowa, January 12, 2016. REUTERS/Scott Morgan

The first-quarter advertising blitz would represent almost a doubling of the proportion of money that the campaign devoted to such spending, on average, during 2015.

The report, prepared by her team’s finance committee, aims to paint a picture of a fiscally prudent campaign operation that has been spending heavily on digital tools and organizing last year and is now ready to ramp up ad spending as the 2016 White House race moves into a critical new phase.

“The significant early resources mobilized by our Finance Committee in 2015 helped us make smart early investments in key areas – and will enable us to continue with strategic allocations in Q1 of 2016,” the report reads.

The first quarter is a crucial period in the presidential nominating contest. It kicks off with the Iowa caucus on Feb. 1, followed by the New Hampshire primary on Feb. 9 and a series of other early votes through March, including “Super Tuesday” on March 1 when 11 states hold nominating contests.

Many of the contests during March, the report notes, “are in big states with expensive media markets.”

In 2015, the campaign devoted nearly 10 percent of its spending to technology and digital tools, about a fifth of the budget on list-building and almost another quarter on state organizing, according to the year-end document.

List-building refers to amassing names of potential voters who a campaign wants to woo.

The Clinton campaign declined to comment on the spending report.

The increased focus on advertising spending comes as the campaign expects to shrink the ratios of spending in other areas, especially those that appear related to infrastructure.

State organizing, for example, is projected to go from 23 percent in 2015 to 18 percent in the first quarter of this year.

List-building is expected to go from 21 percent in 2015 to 14 percent in the first three months of 2016.

The report comes two weeks before the Iowa contest, with Clinton locked in a tightening race with Sanders, the fiery U.S. senator from Vermont who has been drawing big crowds in the early-voting states with his calls to crack down on Wall Street.

The emphasis on fiscal prudence is part of a broader effort by the Clinton campaign to reassure supporters that it has learned from her 2008 campaign, which was plagued by missteps, including a failure to match the organizational and digital prowess of Barack Obama, who ultimately won the Democratic nomination - and the general election.

Clinton’s campaign raised more than $112 million last year for the primary fight, according to a previously released statement from Jan. 1. That includes $37 million raised in the fourth quarter.

The campaign had nearly $38 million in cash on hand headed into this year, according to the statement.

The year-end report only notes budget categories as a percentage of total spending and does not include dollar amounts for categories or line items. Nor did the document include a dollar amount for the overall budget.

Through the third quarter of last year, the campaign spent more than $12 million on direct marketing, online ads and media buys, according to campaign finance filings.

Federal Elections Commission filings for the fourth quarter for all presidential campaigns are due Jan. 31.