While he's done a couple Tea Party rallies in AZ, NV and OH, he's been described as having a history of antagonistic remarks regarding the movement.
I don't know the Kansas group but I'd like to know whether Santorum's trying to avoid something here.
Candidates sometimes choose the smaller venue because it is easier to provide security there.
Rick Santorum has received threats against him and his family.
Maybe he is just playing it safe.
I don't think it is Santorum's responsibility to give a continuous readout on his campaign strategy. No one else is doing this and why would they? Campaigns make scores of decisions every day. That is their business.