The article deals with the fields of activities of the basic Polish political parties in the period of elections to Sejm in the autumn of 1930 as the attempt to counteract the authoritarian strivings of sanacja. The research is based on some unpublished materials of the Polish archives, press and the VIP information agency.

There are described the situations when the figures of the Polish opposition were put into the Brest prison, stayed there and were released from it in the period of the election campaign in September-October of the 1930.

There is revealed the role of the left and centrist parties in the Centolew slate in the period of parliamentary elections of the 1930 in Poland according to the following signs: idea influence on the slate’s programme, pre-election activity and the quota of candidates in the election lists of the slate.

Based on program documents and publications of the main political camps in period of sanacja regime in Poland, an analysis of the changes of mutual perception of these camps, including sanacja camp, and thereby shows the changes in the balance of political forces in the country.