Could the Republicans have won in 2008?

[Stranger in a strange land]

Yes. If Guiliani had won and ran in 2006, a John McCain/Rudy Guiliani ticket could deliver a heavy challenge to Obama.

Read up on Giuliani's 2008 Presidential Campaign, arguably the most embarrassing example of a failed presidential campaign of all time. Giuliani started off as a National Hero who was leading in the polls. He ended as the punchline of a bad joke who had spent $63 million on his campaign to win one (1) delegate.