President Trump raised more than $30 million for his re-election in the first three months of 2019 and now sits atop more than $40 million, his campaign said on Sunday.

Mr. Trump’s campaign — which has set an ambitious $1 billion goal for the 2020 race — launched an aggressive fund-raising push earlier than his predecessors. The campaign has already installed a headquarters in Northern Virginia and is combining a push for both big donations and small contributions online.

Nearly 99 percent of the donations in the first quarter were for $200 or less, according to the campaign, with an average contribution of just over $34.

Some Democrats are concerned that Mr. Trump will spend the next year amassing a war chest as Democrats fight among themselves in a primary now featuring nearly 20 candidates. Mr. Trump’s $30 million haul is about the size of what Senators Bernie Sanders and Kamala Harris — the top two Democratic fund-raisers so far in the 2020 field — raised combined in the first quarter.