The entry of a Southern governor with enough credibility to matter has had the predictable effect on South Carolina primary voters in the latest PPP survey.  In June, Mitt Romney had a 15-point lead in their survey, but Rick Perry now leads by 20:

There might not be a state that betters symbolizes the fundamental shift that’s occurred in the Republican Presidential race over the last few months than South Carolina. When PPP last polled there in early June, Mitt Romney led everyone in the field by at least 15 points. But now with Rick Perry’s entry Romney has lost almost half of his support. That leaves Perry with a 20 point lead- he’s at 36% to 16% for Romney, 13% for Michele Bachmann, 9% for Herman Cain, 8% for Newt Gingrich, 5% for Ron Paul, 4% for Rick Santorum, and 2% for Jon Huntsman.

Voters on the far right side of the Republican spectrum have been dying for a candidate they can call their own and Perry is filling that void. With folks describing themselves as ‘very conservative,’ which is the largest segment of the GOP electorate in South Carolina, Perry’s at 44% to 14% for Bachmann, with Romney mired in single digits at 9%.

That furthest right group of voters has never been all that friendly to Romney though. What has to be a greater sign of concern for him is that with those labeling themselves as only ‘somewhat conservative’ he still trails Perry 37-19 with Bachmann at 11% and Cain at 10%. When Romney’s primary threat was Bachmann he was still winning this group of voters. But Perry seems to be filling a void for voters looking for someone more conservative than Romney and more credible than Bachmann and if he can sustain his lead with that segment of voters he’s going to be tough to topple.

Romney does continue to be the favorite of moderate Republicans, leading Perry 26-20. But since those folks only account for 16% of the overall GOP electorate having their support isn’t going to take Romney very far.

It’s not really that complicated.  Southern voters tend to trust Southern governors more.  Romney seemingly dodged a bullet when Mike Huckabee took a pass, as Huckabee competed strongly in South Carolina and finished second, well ahead of Mitt Romney who received a little more than half the votes Huckabee got.  (John McCain won the state and 18 delegates, while Huckabee got the other six.)  However, now that Perry has jumped into the race, Romney might have preferred that Huckabee stuck around.  Two Southern governors would have split that impulse in South Carolina and might have allowed Romney to win a key conservative state.

Of course, we have almost six months before South Carolina Republicans go to the primary polls.  Perry may not keep the surging lead he has won since his entry.  At the moment, Perry is introducing himself to primary voters in key states like South Carolina, Iowa, and New Hampshire.  Clearly voters are responding positively to the introduction, and Perry has a long record of success in running Texas as a big initial introduction, especially on jobs and economic policy.  Romney and the other candidates in the race have moved well beyond introductions and into policy, which Perry will have to do soon.  He may lose some momentum as his policy choices become clear, especially when Perry starts participating in the debates as he will on Labor Day.

If these numbers hold up — or even stay close to this trajectory — it will effectively close off any hope that the other candidates in the race now can make it anything more than a two-man contest.  Even if Michele Bachmann wins Iowa, the only other state in the early running where she could gain any traction would be South Carolina — but Perry is winning her natural voting base, along with a big chunk of Mitt Romney’s.  If Palin jumps into the race, she would need a surge larger than Perry’s in South Carolina, as she only gets 10% now — and she has a lower favorability rating than Perry (+26 to +40, respectively) and only 9% are unsure about her, as opposed to 20% for Perry.

A Perry win in South Carolina also ends any hope of a quick win for Romney.  And if Romney’s strategy is to wait for a Perry implosion, he may end up waiting for a very long time, as Perry has won many more campaigns than Romney has even attempted, and he’s lost fewer of them.