We’ve been hearing about “Marcomentum” all week, and the endorsement of Nikki Haley was expected to have boosted Marco Rubio’s fortunes in South Carolina. Donald Trump’s eruption at the generally well-liked George W. Bush was supposed to hurt him in the Palmetto State, too, but until today, there seemed to be very little evidence of either in polling. A new poll from the Fox affiliate in Atlanta (via John Ziegler) shows Marco Rubio within the margin of error for the lead, just three points behind Trump at 27/24, with Ted Cruz falling into third with 19%.

Outlier?

A new poll conducted for FOX 5 in advance of Saturday’s GOP primary in South Carolina shows Senator Marco Rubio has jumped into second place to challenge front-runner Donald Trump.

The OpinionSavvy poll conducted for FOX 5 shows Rubio with 24% of the South Carolina Republican voters surveyed, trailing only businessman Trump with 27%.

This week’s endorsement of Rubio by South Carolina Governor Nikki Haley apparently helped push Rubio to the second spot, ahead of Texas Senator Ted Cruz with 19%.

In case you’re wondering, Opinion Savvy is the same firm that had Trump and Cruz ahead of Rubio one week ago today, 36/19/15 respectively. As Allahpundit noted last week, they also came close to getting it right in Iowa, picking up on Rubio’s late surge, even if they missed the magnitude of the vote for all three candidates.

If this is a solid poll, then Rubio has gained nine points in a week while Trump has lost a similar amount, an eighteen-point flip in the gap between the two while the rest of the field stayed relatively static. On the plus side, it has a sample of 780 likely voters, a relatively large sample size for a single state, and “likely” was defined by “I will definitely vote” and those who had already sent in an absentee ballot. On the negative side, OpinionSavvy does not use live interviewers; for landlines, an automated IVR system took the survey, and on mobile, respondents used “an identical survey in visual form.”

NRO’s Henry Olsen discounts this poll and another from Clemson on the basis of skew:

The Opinion Savvy poll says fifty percent of the GOP electorate will be very conservative. No primary has ever had that large a percentage of very conservatives in the voting population, and South Carolina typically has between thirty and thirty-five percent very conservatives. Since we know Trump does less well among the most conservative Republicans, this inaccurate voter sample underestimates Trump’s true level of support.

It’s a good point, but that should benefit Cruz rather than Rubio, right? Cruz is the “very conservative” candidate in the race, or at least that’s the “lane” in which most people envision him. If Rubio gets a nine-point boost from oversampling “very conservative” voters in South Carolina and Cruz’ needle doesn’t budge at all, that would be … strange.

Let’s take this at face value for the sake of argument. If it’s legit, where did the change take place? OpinionSavvy offers a brief analysis of its crosstabs, and a caution against expecting too much from these results:

Rubio has increased his support in several key demographics, including the 45-64 and 65+ age cohorts. Rubio is also ahead of Trump in the Lowcountry, a less conservative area of the state with a lower percentage of Republican voters. In our most recent polls, Cruz has hovered around 19%, which he maintains once again.

Trump has managed to improve his ranking within the youngest demographic, and he maintains the highest commitment from voters: 97% of Trump supporters indicated that they do not foresee changing their vote.

For all intents and purposes, the results indicate a very likely Trump win… just don’t be surprised if Rubio fares better than expected.

If 97% of 27% are firm in their decision, then Rubio will need to find voters from other candidates. Jeb Bush and Ben Carson come in at 11% and 8% respectively, with John Kasich surprisingly in last place at 7%. Some of these voters wondering whether they should switch and jump on the Marcomentum bandwagon — assuming it exists, of course. It seems doubtful that voters will travel in the opposite direction, and also doubtful that Bush and Kasich voters would migrate to Trump — although they might go to Cruz instead of Rubio.

This poll gives Team Rubio a gift, though, in offering the tantalizing hope of a shocking upset victory in South Carolina. That kind of signal late in the game could create a bandwagon effect, especially among those of the anybody-but-Trump mindset. That still requires an actual Marcomentum to exist that voters can see, feel, and hear. If this poll accurately captures that mood, then tomorrow may be very, very interesting. If it doesn’t, then this poll will join many others in the survey graveyard. Until tomorrow night, color me skeptical that the race is this close, but the order may be accurate.

Addendum: The same order is seen in the latest Emerson poll, but the margin is much wider. Unlike OpinionSavvy, they see no evidence of Marcomentum:

In the final day of a three-day tracking poll in South Carolina, momentum is favoring Donald Trump, who leads in the Republican contest with 36% of likely primary voters, up 3 points since Tuesday. Marco Rubio (19%) and Ted Cruz (18%) remain locked in a battle for second. Cruz has seen a 2-point drop since Tuesday while Rubio has stayed at 19%.

John Kasich and Jeb Bush were tied at 10%, and Ben Carson is in last with 6%.

Trump’ support is wide and solid. He leads in all seven of the state’s congressional districts, by margins that range from 4 to 26 points. Trump also holds a commanding lead with both sexes. Men favor him 36% to 18% over Rubio, his closest challenger. Among women, his advantage is 35% to 20%, again ahead of Rubio. Trump even gets the nod from Evangelicals, who prefer him over Ted Cruz, 37% to 23%.

That last from evangelicals has to be a bitter pill for Team Cruz to swallow.