Assuming that the political information provided to the voters directly determines the communication efficiency of the political system in a democratic framework, this paper therefore proposes and tests some hypotheses explaining the politician's behaviour in that respect. Those hypotheses are tested on statements made by major Belgian parties' leaders at the eve of the 1978 and 1981 national elections. Having first related the degree of reserve on the politician's statement with his party's share in the constituency, a positive relationship is found. The second hypothesis states that the degree of reserve in the politician's statement is explained by his reaction either offensive or defensive triggered by the variation in his party's share given the outcome of the precedent election. It is observed that a defensive attitude is adopted by parties having known a reduction of their market share. The third question dealt with examines the infiuence of the size of the party on the abovementioned relationship between the variation of the market share and the degree of reservedness. The results show that apparently the elimination of the size effect does not affect the findings concerning the second hypothesis.