As Democratic candidates begin to file their paperwork to run for president in 2020, they already know they will be facing a well-financed opponent. President Trump’s campaign reported $19.2 million in cash on hand Thursday in a filing with the Federal Election Commission.

The campaign’s three committees reported raising $21 million in the final three months of 2018. That number is on pace with previous quarters last year. And as in previous reports, the campaign relied heavily on donors giving less than $200, raising three out of every four dollars from small donors.

The president’s brisk small-money fund-raising contrasts with the performance of many Republican congressional candidates during the midterm elections, who relied more heavily on donors giving larger amounts as they struggled to keep pace with their Democratic opponents’ fund-raising.

Some Republicans grumbled that Mr. Trump’s campaign vacuumed up donations that could have been used more effectively in the midterms by House candidates trying to retain their seats. The Democrats gained 40 House seats.