When Donald Trump won New Hampshire earlier this month, he made a special point during his victory speech to praise his campaign manager, Corey Lewandowski. This was eight days after Trump lost Iowa, contrary to what late polls suggested -- a loss that was often attributed to Trump's getting beaten in turning voters out to caucus.

"Where is Corey?," Trump said at his moment of triumph. "Does Corey have a ground game or what? Boy, do we have a ground game. Where's Corey? Corey? Corey Lewandowski. You know we learned a lot about ground games in one week. I have to tell you that."

"Ground game" is a term referring to get-out-the-vote efforts: Calling voters, knocking on doors, tracking turnout on primary day. In Iowa, it was clear that Ted Cruz's ground game (a.k.a. "field") was superior. In New Hampshire, Trump argued, his was.

Nah.

Here's what Iowa looked like right before and after the caucuses.

Trump and Ted Cruz ran close for the last few weeks, and Cruz was within five in the final average of the polls. After the caucuses, Cruz won by just more than 3 percent.

It was a close race and the polls were trying to track the notoriously complicated caucus process -- a process that can be affected by strategic turnout. Cruz's win isn't solely the result of his strong field efforts, but it likely played a big role.

"A very, very strong get-out-the-vote effect will be something in the order of 8 to 12 percentage points," Columbia University's Donald Green told us in 2014 when we asked about how much of a difference field could make. Green's done a lot of research on the subject. "That would be a hugely successful face-to-face canvassing operation," he said.

Cruz had a good turnout effort, but it's not clear it fell into the "very, very strong" and "face-to-face" effort -- the latter referring to knocking doors and getting people to the poll site come Hell or high water.

Trump won New Hampshire by 20 points. His "ground game" could have been Corey Lewandowski throwing eggs at school buses, and he would still have won.

Which brings us to South Carolina. There, Trump leads by nearly 17 points.

Unless those polls 1) are very wrong or 2) shift quickly -- both possible to varying degrees -- field isn't going to make a difference, particularly given that South Carolina is a more traditional political process (i.e. show up, vote and leave) than was Iowa. If Cruz closes the gap, maybe. If he doesn't? Very unlikely.

Donald Trump's field effort has been tested once, in Iowa. It failed. It likely won't be tested again in South Carolina.