Rick Santorum ended his own run for the Republican presidential nomination on Wednesday, quickly endorsing Marco Rubio's bid. In an interview Thursday on "Morning Joe," the former Pennsylvania senator showed some rust as a surrogate.

Here's the clip.

Awkward, right?  Asked to name a single accomplishment of Rubio's since coming to the Senate in 2011, Santorum whiffs. Here's a sampling:

If you look at being in the minority in the United States Senate in a year when nothing got — four years where nothing got done, I guess it’s hard to say there are accomplishments...Republicans have been in the majority for one year and one month of which, as you know he was running for president primarily. The first four years he was in the minority and nothing got done.

Part of the problem here is that Santorum isn't now and never has been all that great a surrogate.  In the interview you can see him wanting to pivot to his own record in the Senate and all of the things he accomplished. But, of course, this interview isn't about Rick Santorum, it's about Marco Rubio.

But, another major part of the problem is that Rubio doesn't have all that many accomplishments in the Senate. As Santorum noted -- unhelpfully for Rubio: "Republicans have been in the majority for one year and one month of which, as you know he was running for president primarily."

Of course, a long list of accomplishments in the Senate isn't exactly a problem at the moment for Rubio. Among the 46 percent of Iowa Republican caucus-goers who said they wanted a president who had the "right experience in politics,", Rubio led the way with 39 percent. Ted Cruz, who has been in the Senate even less time than Rubio, was second among those voters with 35 percent. Jeb Bush, the former Florida governor with the deepest political resume in the field, took just 4 percent in that group.

And, the current resident of the White House -- as any Republican will tell you -- had a very brief resume in politics before getting elected, and it didn't seem to affect how voters responded to then Illinois Sen. Barack Obama.

That Obama comparison is, however, potentially very problematic for Rubio -- particularly as the race narrows and the choice between the candidates comes into clearer focus. There remains a skepticism/wariness about choosing a Republican nominee whose political resume is as thin as Obama's was given that much of the GOP believes that the election of the current president was a huge mistake.

“This is like the pitcher in the major leagues: They only let him throw five innings because he’s brand new and he’s raw, and you don’t want to ruin his confidence, so give him a good five innings and get him on the bench,” Christie said of Rubio in an interview with the Washington Post on Wednesday. “He’s not ready to be president.”

Anything that plays into that narrative -- like Santorum not being able to name a Rubio accomplishment -- is bad for the Florida senator. The Rubio teams needs to find a line (or two) -- Obama went with "I haven't spent a lot of time learning the ways of Washington, but I've been there long enough to know that the ways of Washington must change" -- that pushes experience to the side or flips the argument in his favor. Then they need to send that line to Rick Santorum. ASAP.