The temperature dependence of the nematic electroclinic effect has been studied in binary mixtures prepared from two chiral compounds with nematic-smectic A-smectic C and nematic-smectic C phase sequences. The data obtained show a substantial difference in the magnitude of the effect, not only with the type of phase sequence, but also with the temperature range of the subsequent smectic A phase. These results suggest that short-range smectic fluctuations can play an important role in the nematic electroclinic effect at least when a smectic C phase is close to the nematic. In addition, the dynamic behaviour of the electroclinic effect has been investigated in the compound with the nematic-smectic A transition. As in previous work, an anomaly in the electroclinic response time has been found around the nematic-smectic A transition. This fact is analysed qualitatively assuming two different mechanisms contributing to the electroclinic effect.