The CBS web page says it is 7%. I looked. It says that the number of registered republicans is 517(?) to 575. An n of 575 won’t give an MOE of 4% at a 95% confidence level.
I dunno. I’m pretty sure that n=575 should yield around 4-4.5% at a 95% confidence level. Doesn’t even depend too much on what the total population size is.