Trump's campaign is more likely to say anything to ignite his core base than to stand by any particular stance. The need to branch out beyond that base has prompted various flip flops or less vocal support for a number of his promises. This is proof that he has no core convictions, or at least isn't running for the sake of advancing his convictions.
Judging from Donald Trump's behavior and speeches, he has no core convictions. In the conduct of his own business he has acted against the interest of his investors and employees, has gone bankrupt several times, borrowed vast sums of money, and built ugly buildings. His only motivating conviction is his own self-interest.
No, Donald Trump does not seem to have any core convictions. He can speak passionately about an issue at a given moment, but he often backs away from it later. Trump doesn't seem to operate from any internal barometer. He measures his success as well as his opinions by the reactions of those around him and his popularity.
No, he does not hold any core convictions, he simply says what he thinks will get him votes. If he would win as a Democrat, he would run as a Democrat. He will always do and say what gets him ahead, even if it hurts those around him. This is how he built his empire.