Yes, I would certainly say so. Had McGovern lost Massachusetts in 1972 and had Mondale lost Minnesota in 1984-the only states that they won-Washington D.C. would have prevented them from being shut out of the Electoral College. And the heavily Democratic status of the District is the main reason why Republicans are opposed to D.C. statehood, because it would give the Democrats two Senate seats which they would hold in perpetuity, and would only lose in the event of a Roy Moore-level scandal or worse. Those seats could very well constitute the balance of power in a closely-divided Senate, and swung it in the Democrats' direction.
Not even that would be enough for a GOP win in DC. Since the GOP would have no chance of getting a third of the vote (assuming it even ran a candidate), the Democrats could orchestrate a write-in campaign without fear of losing due to vote splitting.