Pat Buchanan would have done better than Dole? Give me a break. He was just too racist, too anti-Semitic and too much of a gadfly to meet the minimum requirements for a President. He would have lost a historic landslide.
2008, I think Romney would have fared better than McCain.
Granted, he would not have won (no one could have beaten Obama that year), but he would have been competitive.
When the economy collapsed and the government starting bailing out banks for 700 million, all the other issues, like terrorism and Iraq, became nothing.
That's where McCain lost his appeal. With his military background, McCain was a guy who could win in an election dominated by national security. In an election dominated by finance, McCain was done.
But Romney has an economic background. He was a businessman. He was a governor. He would've made a solid argument that he was better equipped to handle the Great Recession than some "inexperienced" senator from Chicago.
McCain lost by 7%. Romney would have lost by around 4-5%. He would have taken NC and Indiana (as he did in 2012) and maybe Florida.
And also, Romney would not have picked Palin.
That would be the biggest advantage for a non-McCain candidate in 2008. And I suspect it would have helped the Republicans somewhat.
However, you have to wonder whether being tied to the banking industry and private equity world would have actually hurt Romney. Rather than being seen as an "economist," he could have been seen as akin to one of the reckless financiers at Lehman, AIG, Goldman, etc. That could have made Romney's finance background a liability rather than an asset. That argument certainly didn't seem to win over many people in 2012 anyway.