Guys, no one has run a serious ad campaign against Trump since he's gotten into the race because they're all scared to alienate his supporters.
Hillary will not hold back one bit and her campaign team will absolutely tear Trump to pieces over the air. Not to mention, Trump is going to have to spend a lot of political goodwill to earn the support of conservatives that loathe him almost as much as Hillary for his attacks on Cruz and his inconsistencies, as well as Bush style neoconservatives who consider him a national security threat. The Democratic race is much tamer, and Sanders will likely give his full throated endorsement to Hillary when he loses.
Trump might have a real shot if he can win the nomination by the end of March and if Sanders can drag out the race enough where it starts to get really nasty. He could consolidate the GOP in time in that situation, but if Cruz and Rubio can prevent Trump from winning it before the convention, it'll be a McGovern/Goldwater repeat.
I think something people don't often think about is the money issue. Trump says he's self-funding, but does anyone really believe he will begin liquidating his assets to fuel his campaign? It will take many hundreds of millions, likely far beyond the amount of cash-on-hand he has. I can't see him doing this if he even remotely thinks he could lose. I get that he's been cheap in the primary probably to save money, seeing as he doesn't need to spend to win, but in the general election, he absolutely cannot win without pouring enormous money into the states.
Further, he can't depend on big dollar support from the GOP's usual donors. A lot may see him as a wasted investment, or simply despise him so much that they won't help. Plus, a lot of that money would go to Super PACs anyway, which are being seen as a complete failure this cycle, so that doesn't help either. And if he did take their money, he throws away one of the most powerful reasons people like him: He's self-funding and not beholden to any donors. He can't really run a successful small-donor campaign either, because he's made it clear he's super rich and super successful, and asking the pooooorrlllly educated for money would really undercut that narrative.
Every single thing here points to him running a cheap, hamstrung campaign that will cost him dearly on election day. Either that, or he takes lots of special interest money to keep his campaign above water, and people finally see him for the lying fraud he really is, and thus also pays dearly on election day.