Hearings for Betsy DeVos, Mr. Trump’s choice to lead the Department of Education; Andrew Puzder, his labor secretary nominee; and Representative Mike Pompeo, Republican of Kansas, Mr. Trump’s pick to lead the Central Intelligence Agency, have all been pushed back as Democrats clamor for more time to collect and review the standard background checks that nominees traditionally undergo before their hearings commence.

Wilbur Ross, Mr. Trump’s pick for secretary of commerce, will also be delayed several days because his ethics agreement is not complete, according to the chairman and ranking Democrat of the commerce committee.

The delays represent a stumble for the incoming Trump administration, which has vowed to run government with a businesslike efficiency, and highlights how in several respects its preparation to take office is behind that of predecessors.