We started getting some clarity in the Republican and Democratic races Saturday night. Hillary Clinton squeaked out a win in Nevada — but did so in a way that suggests she has, despite Bernie Sanders’s strength, maintained her national advantage. Marco Rubio’s strong showing in South Carolina helped push Jeb Bush out of the race, giving Mr. Rubio a chance to unify the mainstream of the Republican Party and bring about a true three-way race.

Republican Primary in South Carolina

When Donald Trump won New Hampshire, he won it in two ways: He won the most votes, while the establishment was divided by a split result among its ranks.

Tonight, Mr. Trump won with nearly the same share of the vote. But he might lose once and for all what has been his biggest advantage: the divided Republican field.

With 99 percent of the vote reporting, Mr. Rubio holds 22.5 percent of the vote. It might not seem an impressive figure, but it meant he finished well ahead of Mr. Bush, who holds just 7.8 percent of the vote. It was enough to force Mr. Bush out of the race.