It seems likely that Donald Trump is headed for another win today – but a closer one than I would have expected even a few days ago. In 4 polls taken February 16-19*, the medians are Trump 33%, Rubio 20.5%, Cruz 18.5%, Bush 9.5%, Kasich 8.5%, Carson 6%. Rubio may do even better than these numbers would indicate, since his surge is quite recent.
The graph at left shows the running median, which I estimated day by day. In a significant trend in the last week, many Trump and Cruz supporters got on the fence after the debate on the 13th, which was an insult-laden spectacle. Trump has slowly leaked 5.5 points of support and Cruz has lost 2 points (and Kasich gained a few points).
Then, on Wednesday February 17th, South Carolina Governor Nikki Haley endorsed Rubio. Immediately after, Rubio surged by 5.5 percentage points compared with 7 pre-endorsement polls, Feb. 13-17 sample, showing a median of 15.0 ± 0.5%.
Even the newest polls still have at least half their sample coming before the Haley endorsement. So Rubio will likely outperform them, and maybe get into the mid-20s. Trump is in the news again for going after Pope Francis on the 18th an unbelievable event all by itself. I think Rubio is headed for a strong second-place finish. Seems like he’s got some life in him yet.
Trump will probably still hang on to first place. That should give him at least 44 of South Carolina’s 50 delegates. Given the all-or-none nature of delegate assignment (29 statewide delegates and 7 Congressional districts of 3 delegates each), Rubio could pick off a district or two.
Haley’s bigger impact might be driving Jeb Bush out of the race. If she had endorsed Bush, the results would probably look more like a four-man race. The ongoing presence of Bush, Kasich, and Carson is a drain on Cruz and Rubio because of delegate-assignment rules in the next few weeks, which often have a 15-20% threshold requirement. The more candidates remain, the more likely it is that Trump can get a majority of the delegates between now and Super Tuesday on March 1st. I previously wrote that Super Tuesday is a deadline for the Republican Presidential field to narrow. If Haley helps accomplish that, it’s a substantial contribution to her party’s Establishment wing.
*The nominal one-sigma uncertainties on the medians are 1.6-2.0% for Trump/Rubio/Cruz/Kasich, 0.7% for Bush/Carson. I excluded a Harper (R) poll that did not have any sample post-Feb. 17th.