The SurveyUSA is a combo of robo-poll calling (landline) and online surveys of 606 "likely" voters. As it reports in the fine print:
This research was conducted using blended sample, mixed mode. Respondents reachable on a home telephone (70% of likely voters) were interviewed on their home telephone in the recorded voice of a professional announcer. Respondents not reachable on a home telephone (30% of likely voters) were shown a questionnaire on their smartphone, tablet or other electronic device.A "gold standard" poll, in which people are called by live human beings at both their landline and cell phones, will be released later this week by the AJC. Pay attention to that one.