Because 50% of the population, ie women, have been completely offended and alienated by him. You cant overcome those maths, and he has no Hispanic votes
Trump has plenty of women voters there are plenty at his rallies, however more women have always voted Democrat than Republican. In New York Trump is polling 50 points ahead of Cruz are there no women in New York? There is a reason the entire US media is against him, why republicans are spending millions trying to stop him, its all about the money. They know Trump will cut off the money supply to lobbyists via a corrupt political system and look at politically motivated procurement in heath and the military, every vote against him is another vote for the Establishment and corrupt government.
On policy why should 11 million people be allowed to stay in the US who have entered illegally?
What is wrong with building a wall to keep out illegal drugs and illegal immigrants?
What is wrong with a tax free income tax threshold of $25,000 for singles & $50,000 for couples?
What is wrong with bringing jobs back to the US and fairer trade with China, Japan and others?
On the abortion question, it was a hypothetical question based on abortion being illegal and he answered it. He later qualified his answer something Hillary has done repeatedly without criticism, no one died. Hillary said very recently no American died in Libya when 4 American did actually die in Benghazi but this was largely ignored by the anti Trump media. It appears to the media stopping Trump is more important that 4 American lives lost.
All these things Trump is now being accused of from racism to being anti women only started once he entered the race, it was no problem when he presented the Apprentice. Truth is that it was no problem because it not true then as it is not true now.
People get the politicians and the country they vote for, it is sad that in Trump they have the opportunity to vote for a man who is uncontrolled by special interests and is running for the people, he certainly does not need the death threats and hassle. Successful or otherwise Trump has revealed the US to be anything but democratic and a place where people votes do not matter to the political elites that really run the country. Those that oppose him are doing the work of the Establishment for them and condemning themselves & their country to years of the same.