Ryan and DeMint are politicians. They are better than some, but they are still politicians. Most of the conservatives who are backing Romney are doing so because they think he can win, because thats what the consultants are telling them.
Looks like Paul Ryan isn't above changing the rules or telling a nontruth when it suits his fashion:
UPDATE: Ryan's aides had told reporters on Capitol Hill that his position as president of the RNC presidential trust, a sum of $21 million that the committee turns over to the nominee, had meant he couldn't endorse in the primary, making this a bit of a shift.
What is clear is that Romney's team is hoping for a win in Wisconsin that, whatever the margin, they can use to declare victory and the primary over in the hope of depressing Santorum's numbers in his home state. Santorum's aides have said he plans to keep fighting, that a number of May contests favor him. But if he truly faces the chance of losing Pennsylvania and a poll this past week showed the race statistically tied between him and Romney there Santorum could end up with a tough choice to make about his future.
http://www.politico.com/blogs/burns-haberman/2012/03/ryan-for-romney-119133.html
Once the race reaches Pennsylvania, you can bet that Patty Toomey will line up behind Romney. Remember Patty Toomey came out in favor of repealing Don’t Ask Don’t Tell, right after he was safely elected Senator.