NEW YORK — Third time’s the charm for Donald Trump. For the third Tuesday in a row, the billionaire businessman appeared in the lobby of Trump Tower to ring in a decisive victory. This time, he could assume the mantle of the presumptive Republican nominee, all but guaranteed to carry the party’s banner into November following Ted Cruz’s primary night dropout.The moment capped off the first stage of the most improbable presidential campaign in recent memory, which has brought the businessman from novelty to the brink of the Republican nomination in the course of 10 and a half months.