mongod:3.2.12

os:centos 6.4

A and B node are in the same room，C node in other room ，A.priority=10,B.priority=5,C.priority=1,on the primary node A：cfg=rs.conf();cfg.members[B.node.id]=priority=15;rs.reconfig(cfg);

A node and B node log：VoteRequester: Got no vote from xx.xx.xx.xx:yyyy because: candidate's data is staler than mine, resp

but node is primary 

node A and node B continue to try in Starting an election for a priority takeover,but failed to be primary 

Q1: why the higher priority node A or node B not elected for master?