Typical Margin of error numbers for these polls are in the range of 4 to 6 percent or so. But note that averaging 4 or 5 polls as RCP does will lower these Margin of Error figures for the average.
Also note that the polls are in rough agreement with the average of the polls.
And don’t make the mistake of believing that a candidate who polls 1% with an MOE of 5% is actually polling somewhere between -4% and 6%. That is not how MOE is applied and there is no way a candidate can poll less than zero.
The margin of error is also dependent on the sample size. If the MOE isn’t 3.5 the sample tends to be so large that it makes the poll suspect for accuracy. At least, that’s been my experience in the past.