Fredreka Schouten

USA TODAY

As she closed in on the Democratic presidential nomination last month, Hillary Clinton trimmed her spending sharply, allowing her to stockpile a staggering $42 million in cash reserves for her showdown with Republican Donald Trump.

Clinton spent $14 million in May, campaign-finance reports filed Monday show. That’s down sharply from the nearly $24 million she spent in April, as she waged a two-front battle for the presidency against Trump and her rival for the Democratic nomination, Vermont Sen. Bernie Sanders.

It’s the largest amount of available cash Clinton has amassed during the entire election cycle and has helped her campaign fund an advertising blitz in the early days of the general-election fight. Clinton and her allies are spending more than $23 million on ads in eight presidential battleground states, according to data compiled by NBC News.

Trump, who was slow to build a fundraising operation, is not on the air in key states, according to advertising trackers.

Trump had not released his May fundraising and spending figures as of early Monday evening. They are due by midnight to federal election regulators.

Clinton and a joint fundraising committee she established with the Democratic National Committee raised a combined $28.2 million in May.

Clinton’s biggest line-item: Staff. She employed more than 640 last month and reported $2.4 million in payroll costs in May, according to her filings with the Federal Election Commission. That’s a smaller staff than the campaign had during the height of the primary battle with Sanders. In March, for instance, more than 780 people worked for Clinton, and her payroll costs hit $2.8 million that month.

Clinton’s second-largest May expense: Travel at nearly $2.1 million

Contributing: Christopher Schnaars