Democratic presidential candidate, South Bend, Indiana mayor Pete Buttigieg speaks during a campaign stop on September 23, 2019 in Dubuque, Iowa. Buttigieg is on this third day of a four-day bus trip around the state.Scott Olson | Getty Images News | Getty ImagesSouth Bend, Indiana Mayor Pete Buttigieg brought in $19.1 million in the third quarter, his campaign announced on Tuesday.The haul is less than the sum Buttigieg raised in the previous quarter, but is still expected to be among the heftiest totals raised by any of the candidates vying for the Democratic nomination for president in 2020.In the second quarter, Buttigieg raised $24.8 million. The third quarter is generally a difficult fundraising period.In an email to supporters, campaign manager Mike Schmuhl said the campaign received donations from 580,000 people and had raised a total of $51 million since the start of the year.The campaign said roughly 182,000 people donated to the campaign for the first time in the quarter, which spanned July through September.”This is great news and it positions us to not just go the distance, but win,” Schmuhl wrote. “What we’ve raised has helped us hire organizers and open offices in states critical to winning the nomination. It’s gotten Pete to debate stages. We’ve run ads and been able to move Pete around the country to rally new supporters day by day, week by week.”Buttigieg’s announcement is the first of the major candidates, who are required to file official data with the FEC by Oct. 15. Sen. Bernie Sanders of Vermont, the biggest money-raiser of the field, said Tuesday that his campaign had raised $25.3 million in the third quarter.The nearly $20 million raised by Buttigieg comes as the campaign struggles to regain the early momentum that propelled the mayor of a city of about 100,000 to the top echelons of the Democratic primary contest.Buttigieg is hovering around fourth place in an average of national polls tallied by Real Clear Politics, with 5.3% support. Former Vice President Joe Biden is dominating the field with 27.8% support, while Sen. Elizabeth Warren is in second with 21.5% support. Sanders garners 17.5% support.Amid the slow slide in national polling, the Buttigieg campaign has put special focus on the early states, where it now maintains more than 200 staffers and 42 field offices.The campaign said Tuesday that in Iowa, the first caucus state, it now has a staff of nearly 100. In New Hampshire, the first primary state, the campaign said it has nearly doubled staff from 34 people to 64.