2016: President Romney vs. former President Obama

[Kingpoleon]

275: Fmr. Pres. Barack Obama(D-IL)/Mayor William Bratton(D-NY) - 48.7%
263: Pres. Mitt Romney(R-MA)/Vice Pres. Paul Ryan(D-WI) - 49.2%
Other: 2.0%

Obama has low base turnout due to his narrow primary win against Sen. & Fmr. Gov. Brian Schweitzer. However, he manages a narrow win over Romney due to the declining economy and his rather popular running mate who, despite losing the Vice Presidential debate's main parts of economy, triumphed on national security issues and homeland security.

[Kingpoleon]

If the winning candidate doesn't win the popular vote, it's more likely to be a Republican.

I think Romney would win a relatively close victory in such a scenario (unless there's a GDP growth below 1.5% and/or a serious foreign crises; then Obama would be victorious)

Not true. The EC is slightly in favor of a Dem.