MANCHESTER, N.H. — Perhaps Rick Santorum should have gone straight from Des Moines to Charleston.

A week after his magical finish at the Iowa caucuses, Santorum crashed back to earth Tuesday night with a fifth-place finish in New Hampshire on Tuesday, raising questions about his staying power heading into South Carolina.

The paltry 9 percent he registered here sucks away much of the momentum he earned last week and raises the stakes for his campaign heading into the Palmetto State.

“We wanted to respect the process here. We wanted to respect the fact that we were going to campaign in every single state, states that were good for us, and states that may have been a little tougher,” Santorum said to a small gathering of supporters inside a restaurant ballroom.

Santorum’s decision to spend five days campaigning here — instead of bypassing it for South Carolina — is already being second-guessed as he now faces what’s close to a must-win situation in the first southern primary next Saturday.