He's not worse, just different.
I think Santorum's loss to Obama would be of McGovern scale, costing maybe 100 House seats and a couple in the Senate. Romney will come closer, and some seats in Congress could be saved.
Either way, Obama gets a second term and the system changes.
No. Santorum nearly won Michigan and established himself as a solid conservative, something Mittens can never do.
Having made his mark with conservatives, Santorum has the political skills (many years as a Republican in Democratic Pennsylvania) to reach out to the rest.
Anything slick Romney tries will not be taken seriously, unless he somehow convinces the public that he is a real, genuine “man of the people.” That would be tough.