Strong wins by Cruz and Sanders in Wisconsin make both races a lot more interesting.
Cruz has beaten Trump by 18% (at 59% reported). This is well beyond recent polls.
What will be key is if he wins every congressional district. Trump leads in some rural areas. But if Cruz gains a relative 30+ delegates to Trump, it makes Trump getting a majority a lot harder, and equally he loses momentum. A contested convention is much more likely after today. Trump needs 59% of remaining delegates to get a majority – not impossible with some winner take all states.
Sanders is 12% ahead, which is again more than the polls.
It is still very hard to not see Clinton get a majority of delegates before the democratic convention, but the Sanders camp is arguing super delegates may change their minds. If they can stop her from getting a majority just from pledged delegates, they they may refuse to concede until a vote at the convention. You could have two contested conventions.