I think Romney would be beating Hillary right now. These email leaks would have been fatal against any competent politician with no skeletons. No way he picks Pence as VP.
Romney's main problem in 2012 was that he didn't really have anything solid to run against. Obama was a decent president with no major scandals. Even Obamacare, the Republicans' great bugaboo, was modelled after his own Romneycare.
As a result, Romney had no ammo other than boilerplate Republican talking points. To get any steam at all, he had to resort to lying his ass off.
His big convention theme in 2012 was Obama's "You didn't build that" quote, which was a perfectly reasonable quote ripped out of context and misrepresented.
Seems so absurd today. Romney would be hammering the e-mail scandal and looking like a Boy Scout in comparison.
That said, if Romney were running today, the Russians would not be flooding the US media with hacked Democratic documents, since Romney is as big a Russia hawk as Hillary is.