Not only will Trump probably not win the Republican Nomination outright (he needs 58% of the remaining delegates and is not polling enough to hit a +50% majority of Delegates) it is absolutely impossible for him to beat Clinton or Sanders in the general election based off of every poll anywhere. He's polling worse than any other presidential candidate in over 30 years. He'll lose at something around 60%-40% if he's lucky and the Democrats will take back the Senate at least. They're currently leading in the polls in all 7 contested Senate races lost in off year elections in 2010 but from states Obama carried in 2012.
I highly doubt Trump will even get the delegate votes to win the nomination. Currently he's losing 40% to 60% in non-official polling of pledged delegates for their vote on a second ballot at the Republican Convention and that's from States Trump won in the South who have already held their state Republican conventions. Personally I think once Ted Cruz's name comes out of the sealed documents from the DC madame case next month, it'll be Kasich for the republican nomination.