Donald Trump’s near sweep of states on Tuesday — with the notable exception of Ohio — set up a true three-way race for the second half of the primary season.

The results Tuesday night showed why it’s a race he could win.

Despite his loss in Ohio, Mr. Trump is positioned to make a serious run at earning an outright majority of delegates and avoid a contested convention.

His success in winner-take-all Florida — worth 99 delegates — was enough to push Marco Rubio out of the race. The consequences of the departure are not too significant: Mr. Rubio was already reduced to around 10 percent of the vote, or maybe less, by the time he lost his home state, Florida, by a 19-percentage-point margin.

It was the scale of Mr. Trump’s win that was impressive and telling. He won 46 percent of the vote in Florida and carried every county but Miami-Dade, Mr. Rubio’s home county. He did it in a closed primary, where only registered Republicans are permitted to vote, a format that was thought to put Mr. Trump at a disadvantage.