Probably not a Senator. Generally, Senators travel with little to no security (unless there's some specific reason why they need it -- e.g., a threat or another position they hold/held), so 6 people would be serious overkill. Governors definitely travel with a security detail, but even then, 6 people seems like a lot.

Generally speaking, it's heads of government that have the most security (e.g., President, VP, Governors). Senators and Representatives are replaceable, and there would not be a serious impact on the functioning of the government if one were taken out (symbolic impact, yes; operational impact, no). I always figured the reason for having a security detail for Governors was that it would have a more serious impact on the actual short-term operation of the state's government.