I don’t think Carson has staying power, but there are now five Iowa polls where Trump is losing to Carson and now we have a national poll reflecting a polling decline of Trump’s support. I know we have less than 100 days to go until Iowa, but it’s still early and I’ve seen the lead fluctuate in the last election at one point Herman Cain was the front runner, there’s still plenty of time for some shakeups and surprises - I don’t think Trump is guaranteed the nomination yet.
On the day their poll came out, this came out: Poll: Trump leads Carson by 14 points nationwide!!!