Republican presidential candidate Donald Trump speaks at a rally in Phoenix on Saturday, June 18, 2016. (AP Photo/Ross D. Franklin)

The Republican National Committee took on $2 million more debt in May as it finalized a joint fundraising agreement with Donald Trump's campaign, underscoring how the real estate mogul's lack of a fundraising structure has put financial pressure on the national party committee.

The RNC raised $11 million in contributions for the month, including $3 million that came in through Trump Victory, a joint fundraising committee it set up at the end of May with Trump's campaign and 11 state parties, new campaign finance filings show. The party ended the month with $20 million in the bank -- but also nearly $7 million in debt, up from almost $5 million at the end of April.

Sean Spicer, the RNC's communications director, said that the party's increased line of credit was typical for this point in an election year, adding that party officials were optimistic about fundraising.

"This report only reflects one week of the joint fundraising agreement, and I think as we continue to ramp up, you’re going to see continued enthusiasm from donors around the country," he said.

Still, the RNC is in a starkly different place from four years ago. In May 2012, the national party scooped up more than $34 million, ending the month with more than $60 million in the bank and $9.9 million of debt. Nearly $26 million that month came through Romney Victory, a joint fundraising effort between the party and the 2012 nominee, Mitt Romney.

Trump, who largely self-financed his primary campaign, just began to raise money in earnest during the last three weeks, headlining a series of high-dollar events throughout the country. But top party fundraisers have struggled to get people to bundle checks from their friends and family, and the campaign has been slow to finalize a fundraising schedule for the rest of the summer, according to people familiar with the situation.

The slow money pace comes as the RNC is racing to expand its national get-out-the-vote program, an operation that is even more essential than ever because of the Trump campaign's small footprint on the ground.

GOP fundraisers are hopeful that the billionaire developer will be able to attract support from a slew of wealthy figures who had not backed the party before. Several Trump friends and allies topped the list of RNC donors in May, including Las Vegas magnate Phil Ruffin, who gave $284,600; Los Angeles investor Thomas Barrack, who contributed $299,600; and PGA National developer E. Llwyd Ecclestone and his wife Diana, who together gave $668,000.

However, those large checks cannot all go directly to the RNC's political activities. The large share of the money raised through Trump Victory is earmarked for new party accounts to pay for convention, legal and headquarters expenses. Of the $3 million raised through Trump Victory in May, more than $1.8 million went to those accounts.

Anu Narayanswamy contributed to this report.