A wireless sensor network (WSN), a type of distributed wireless ad-hoc network, is characterized by large amount of sensors and low power supply. In WSN, it is important for sensor nodes to have low transmission delay (due to large number of sensor nodes) and low power consumption (due to limited power supply). In this paper, we propose a new routing and MAC protocol $Cluster-Management and Power Efficient (CuMPE) protocol, to meet the above objectives. The routing part of CuMPE is cluster-based and uses a selective flooding algorithm to propagate transmission cost. Based on the cost information, every sensor in the network tries to establish the minimum cost path to the cluster head. The MAC part of CuMPE first finds the critical path that has the longest transmission delay to a cluster head and schedules sensor nodes using TDMA scheduling to avoid extending the critical path. Simulation results have shown that CuMPE protocol is more power efficient and has shorter transmission delay than existing protocols, such as LEACH, PEGASIS, and HIT.