Honestly, President Romney would've crushed Hillary. He'd have an incumbency advantage, economic improvement, and would be much more favorable than Trump. Hillary would still be bogged down by the email/Benghazi baggage, so Romney plows over her in the general.
President Mitt Romney (R-MA)/Vice President Paul Ryan (R-WI) - 396 EV (54.2%)
Former Secretary of State Hillary Clinton (D-NY)/Senator Mark Warner (D-VA) - 142 EV (44.7%)
A Dem Senate pushing back against those investigations would help her cause substantially. I'm not even sure the public would find out about the private server. Note that I still have a bigger R win than 2004 for Romney, though.
You think they would net lose 3 seats in a 2014 midterm with a Republican president? Even with the bad map for them, Romney would need >55%, maybe >60% approval.
I'm just not sure what seats they'd lose. I could see Kansas going for Greg Orman (who never said who he'd caucus with), Georgia going for Michelle Nunn, and
maybe Kentucky going for Alison Grimes. Montana, South Dakota, and West Virginia were almost guaranteed Republican pickups. So the GOP has essentially balanced out whatever gains the Democrats could've made by picking up those three seats.
Edit: Here's a map of 2014 under Romney. Light colors denote pickups, dark colors denote holds.
