IOTL Romney was the runner-up in 2008 and the nominee in 2012. He did slightly better than McCain, but the Obama administration was something of a disappointment even to its own supporters and there were headwinds against the GOP in 2008. McCain probably had more personal appeal as a pol than did Romney. His career electoral record is at least more impressive. Romney loses in 2008 by a slightly bigger margin than McCain did.
In 2012 the runner up was actually Rick Santorum, but in recent presidential elections the Republicans have developed the practice of having an "evangelical candidate" who gets a large share of the primary vote without really having a chance of being nominated (Huckabee, Santorum, Cruz). The next runner up after Santorum was Newt Gingrich. The nominee in 2012 in descending order of probability is Gingrich, Santorum, or Romney again. Only Gingrich has a chance of winning the general election, and that chance is very slim. A President Gingrich timeline has possibilities.
In 2012 the runner up was actually Rick Santorum, but in recent presidential elections the Republicans have developed the practice of having an "evangelical candidate" who gets a large share of the primary vote without really having a chance of being nominated (Huckabee, Santorum, Cruz). The next runner up after Santorum was Newt Gingrich. The nominee in 2012 in descending order of probability is Gingrich, Santorum, or Romney again. Only Gingrich has a chance of winning the general election, and that chance is very slim. A President Gingrich timeline has possibilities.