The problem is that is prohibits the typical Republican committee campaign style. The campaign theme has been an attack on some specific issue that concerns the public for some strange reason: Willie Horton ad, Swift Boat ads, Truther ads. Rather than present a Republican approach, especially the recent campaigns have been totally focused as attacks. This year, they knew that Hillary was popular, as was her husband. They spent the past four years doing nothing other than attacking Hillary. They have had about three or four different committees investigate Benghazi. When that didn't work, they investigated Benghazi emails. The focus has been totally on destroying her credibility with a Swift Boat type approach on the Benghazi thing.
What Trump has done has been to define that HE can't run on that issue. He is on tape too many times with the opposite opinion.
Pretty sure Trumps praise of Hillary is from when she was the Senator from NY. Anyway, again it's a positive he wouldn't run on those fake issues during the general election. Independents are smart enough to laugh them off. Benghazi is only considered a relevant issue by the 40% brain dead die hard right wing lemmings who will believe anything and vote for any dummy on the GOP ticket.
The best thing Trump is on record of saying is around 2004 when asked why he switched the democrat, he said "because the economy performs better under democrats". It's a 100% fact. Things like that won't hurt him in a general election. They will hurt him in the primary.