Nate Cohn

Wisconsin’s highly engaged voters routinely post some of the highest turnout numbers in presidential elections. On Tuesday, they will play an important role in both major-party nominating contests. Here's what to look for.

Donald Trump’s presidential candidacy has stunned the Republican Party. But if he survives a late revolt by his rivals and other leaders to become the party’s standard-bearer in the general election, the electoral map now coming into view is positively forbidding.

Voters in 12 states go to the polls Tuesday as Donald Trump and Hillary Clinton, who have had the most success in the early nominating contests, look to extend their delegate leads over their nearest rivals.

Polling, of course, is not perfect. It’s more challenging in primaries than in general elections, where there are far fewer undecided voters and where turnout is more predictable.