Donald Trump is leading Iowa according to the latest Des Moines Register poll. But his lead is within the margin of error, and there is plenty of reason to suspect the electorate is still very fluid.

TRUMP: 28

CRUZ: 23

RUBIO: 15

1) TRUMP'S LEAD IS VULNERABLE TO TURNOUT WEAKNESS

Trump's lead is five points in this survey, that's smaller than other recent surveys. It is widely assumed Ted Cruz will have a strong turnout operation (which is more crucial in caucus states than in primary states), and that Donald Trump will have a weak one. If these assumptions are true, that five point lead should be considered a tie — especially given the 4.4 percent margin of error in the poll.

2) NEARLY HALF OF ELECTORATE IS PERSUADABLE

While only 10 percent of respondents declared themselves uncommitted or unsure, a lot more are actually up for grabs. A full 45 percent of respondents said they "could still be persuaded" to change their mind. This corresponds with my experience talking to voters this weekend.

Trump supporters and Cruz supporters are less persuadable, more committed than average voters — 71 percent and 62 percent respectively, say their mind is made up. Rubio is just below average. That suggests that the remaining third of the electorate — those backing Ben Carson and the minor candidates — are only 41 percent mind made up.

That puts about 14 percent of the electorate weakly attached to a minor candidate. There's no guessing where that goes, but ...

3. RUBIO IS HAS THE MOST UPSIDE POTENTIAL

Rubio wins on the second-choice contest, with 20 percent to Cruz's 17 percent (Trump is in 4th place with 7 percent).

Rubio has pulled ahead of Cruz in favorability (Carson is in first place in favorability). Rubio, at 21 percent, has the lowest unfavorability of anyone. Cruz's favorables have fallen by 9 percent in the past month, but he's still at 63 percent favorable.

When asked whether voters would be enthusiastic or "okay" with Rubio as the nominee, 58 percent said yes, putting him in a first place tie with Ben Carson. Cruz was third place with 56 percent. A full 37 percent said they would not be okay at all with Trump as the nominee.

Timothy P. Carney, The Washington Examiner's senior political columnist, can be contacted at tcarney@washingtonexaminer.com. His column appears Tuesday and Thursday nights on washingtonexaminer.com.