The problem is Romney like Hillary was badly damaged in the primaries especially by Newt Gingrich and the 20 debates.
To make up for that Romney should have done this
1. Choose Marco Rubio has his VP
2. Bring up the Reagan recovery more and compare it to the Obama recovery
3. Dont say the 47% comment
4. On immigration , remind people that Obama had a filibuster proof majority and didnt do anything, and his immigration policy is PRO LEGAL IMMIGRANT(which it was)
5. Put obama on the defensive
-How does that help him win Ohio, a state which is now (probably ludicrously) considered a solid Republican state by the denizens of Atlas?
To make up for his weaknesses, Romney shouldn't have bothered with his cutsey business conservative/Bushian message. He should have discarded it for the garbage it was. People saw him as an out-of-touch elitist. He should have brushed up on his populist cred.
Populist cred caused Trump to lose votes compared to Romney (compare Trump's 45.9% to Romney's 47.2%); he simply got lucky that Hillary declined from Obama as well. (Though Trump '16 compared to Obama '12 does do slightly better in the electoral vote; Trump gains Ohio and only drops NE-2). Romney's platform had more support from the voters than Trump's.
There was far more third party vote in 2016. Trump got over a million more votes than Mitt Romney.