7-bedroom Charles Village townhome with downstairs apartment on the market for $749,000

John Delaney

Don, the builder

Don, the builder

If President-Elect Donald J. Trump is the dealmaker that he claims to be, sometime between now and Jan. 20, he ought to stop by the Longworth House Office Building's Room 1632 and ask for John. The two men might find they have a few things to talk about.

That's because Maryland's 6th District Rep. John K. Delaney, a Democrat, has been a leading voice in his party for leveraging greater private investment in the nation's failing infrastructure — its roads, bridges, airports, water and sewer systems, rail lines, schools and the like. During the campaign, Mr. Trump touted his own plan to increase such spending by $1 trillion over the next 10 years, chiefly through...