Don’t be surprised if Pete Buttigieg produces an eye-popping fundraising figure when the second-quarter campaign cash numbers start pouring in at the beginning of July.

Earlier this year the 37-year old South Bend, Indiana mayor surged in the polls – moving from the longest of long-shots to a serious contender for the Democratic presidential nomination.

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Now, Buttigieg is keeping up a frenetic pace as he hauls in campaign cash, with the aim of becoming one of the top fundraisers in the historically large field of Democratic White House hopefuls.

“We’re feeling good,” a source close to Buttigieg’s campaign told Fox News, when asked about the campaign’s second quarter fundraising efforts.

To date, much of the fundraising spotlight has shined on former Vice President Joe Biden, the clear front-runner right now in the nomination race. Biden hauled in $6.3 million in his first 24 hours as a presidential candidate and teased earlier this week that his campaign’s received contributions from 360,000 people, with an average donation of $55. Do the math and that works out to $19.8 million.

Biden made the news as he headlined three top-dollar fundraisers in New York City, which likely netted his campaign at least an additional $1 million.

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But Buttigieg is also aggressively courting big-dollar donors, holding fundraising events in recent weeks in New York City, Washington, San Francisco, Miami, Houston, Atlanta, Minneapolis, and on Thursday in Boston.

Buttigieg’s scheduled to headline another top-dollar finance event next week in Miami, ahead of the first round of Democratic presidential primary debates. And he’s planning another in New York City, just before the second quarter of fundraising ends on June 30.

Like Biden, Buttigieg’s is seeking both high-dollar and low-dollar contributors.

The source, who asked to remain anonymous to speak more freely, highlighted that the campaign’s using “an all of the above fundraising strategy, from small-dollar online donations from emails and social media, all the way up to maximum contributions and having people raise money on our behalf.”

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The campaign’s strategy was evident Thursday in Boston, where Buttigieg headlined a fundraiser with top-dollar donors and bundlers before serving as the main attraction at a grassroots finance event.

“These are events that do give people access to the campaign and the tickets for these events start at $25… so as many people as possible get to meet Pete. It’s trying make the campaign more accessible to more people,” the source explained.

The strategy seems to be working. The campaign confirmed that it raised $7 million in April – which was as much as Buttigieg raised during the entire January-March first quarter of fundraising.

Campaign cash, along with polling, is an important metric to measure a candidate's popularity and his or her campaign's strength. Fundraising dollars can be used by campaigns to hire staff, build grassroots outreach efforts, travel and pay for ads.

And that money is helping Buttigieg quickly expand the size of his campaign as he catches up with his top rivals for the nomination. On Friday, the Buttigieg campaign announced they doubled their staff in the first-in-the-nation primary state of New Hampshire – from six to twelve people.

"We've been encouraged by our grassroots support from all over the country. Every contribution, whether it's people's time, energy, or resources is helping shape and build a campaign focused on ushering in a new generation of leadership that Pete represents,” Buttigieg national press secretary Chris Meagher told Fox News.

Biden and Buttigieg aren’t the only candidates to aggressively court big-bucks donors while also hauling in grassroots contributions. Sen. Kamala Harris of California and former Rep. Beto O’Rourke of Texas are both holding top-dollar fundraisers in cities across the country while also raking in large sums online.

But for Buttigieg, the goal of the fundraising frenzy is to put him on par with his much better-known rivals.

“Our plan was that we’d be spending the spring and summer just getting our name out there,” he told Fox News earlier this spring.

Now, the infusion of campaign cash can help Buttigieg with the mission ahead.

“We’ve got a lot of work to do, blocking and tackling work on the ground, the field organizations we’re building up in the early states and that’s what’s really going to decide whether we can win beginning with the first votes that happen early next year,” he emphasized.