Last night, I had high praise for Republican Vice Presidential nominee Paul Ryan’s acceptance speech, because I thought it represented a very strong critique of President Obama’s time in office. And today, I defended Ryan against liberal critics who have been trying to portray the speech as a pack of lies. But that doesn’t mean I didn’t have problems with it.

As I wrote in a column earlier this month, I’ve become increasingly concerned with the way the Medicare debate is playing out during the election. Though there’s a valid critique to be made about the fact that Obama cut Medicare by over $700 billion to finance a new entitlement, there’s a risk to making that the focal point of the GOP health care argument. It’s one thing to accuse Obama of hypocrisy or fiscal recklessness. But it’s another thing to speak of protecting Medicare as if it’s sacrosanct, because that only reinforces the third-rail status of the program.

Ryan himself understands that. In an interview with Ryan in 2010, I pressed him on this point when Republicans were exploiting the issue and he agreed that, “we have to be careful about how we use our rhetoric so we don't dig ourselves into an unsustainable fiscal path."

But I thought that Ryan crossed over the line last night when he spoke in terms of an “obligation we have to our parents and grandparents” and vowing to “protect and strengthen Medicare, for my mom’s generation, for my generation and for my kids and yours.” He also said that, “Mitt Romney and I know the difference between protecting a program, and raiding it.”

That could easily be heard as a promise not to touch Medicare, especially since it wasn’t accompanied by any attempt to sell a reform plan. As Reason’s Peter Suderman notes, Ryan has spent his career performing a delicate balancing act between being a bold reformer and loyal party solider. Conservative fans of Ryan must grapple with the fact that like many Republicans, he voted for the big spending of the Bush era, including the Medicare prescription drug plan. But his conservative critics must grapple with the reality that his tendency to be a loyal solider helped get him to the leadership position that enabled him to advance the cause of entitlement reform. Now that he’s being assimilated into the Romney campaign, the question is whether the balance has now tilted toward being a loyal soldier and away from being a reformer.

Speaking of Medicare during his speech, Ryan declared, “Ladies and gentlemen, our nation needs this debate. We want this debate. We will win this debate.” 

But how they win the debate is important. If they do so by convincing Americans that Medicare is untouchable, they may find it very difficult to do what’s necessary to fix it once elected.