The numbers are broadly accurate, but the lack of attention to them is for good reason: Neither president bore responsibility for changes in the federal debt in his opening month in the White House. The slight decline cited by Mr. Trump — a drop of 0.06 percent, according to Treasury data — is a temporary fluctuation, not a change in direction.

The federal debt is determined by the government’s decisions about taxing and spending, and by the strength of the American economy. The debt was increasing rapidly in early 2009 because the economy was in free fall, and because of policy decisions made during the administration of President George W. Bush.