The majority of the deputies to the Constituent Assembly who had for some time been elected had arrived in Petrograd, and the Bolsheviki always retarded the opening. The Socialist-Revolutionist fraction started conferences with the other fractions on the necessity for fixing a day for the opening of the Constituante, without waiting the good pleasure of the Commissaries of the People. They chose the date, December 27th, but the opening could not take place on that day, the Ukrainian fraction having suddenly abandoned the majority to join themselves to the Bolsheviki and the Revolutionary Socialists of the Left. Finally, the government fixed the opening of the Constituent Assembly for the 5th (18th) of January.
Here is a document which relates this fight for the date of the opening of the Constituante:
Bulletin of Members of the Constituent Assembly Belonging to the Socialist-Revolutionist Fraction. No. 5, Dec. 31, 1917.
To All the Citizens:
The Socialist-Revolutionist fraction of the Constituent Assembly addresses the whole people the present exposé of the reasons for which the Constituent Assembly has not been opened until this day: it warns them, at the same time, of the danger which threatens the sovereign rights of the people.
Let it be thus placed in clear daylight, the true character of those who, under pretext of following the well-being of the workers, forge new chains for liberated Russia, those who attempt to assassinate the Constituent Assembly, which alone is able to save Russia from the foreign yoke and from the despotism which has been born within.
Let all the citizens know that the hour is near when they must be ready to rise like one man for the defense of their liberty and their Constituent Assembly.
For, citizens, your salvation is solely in your own hands.
Citizens! you know that on the day assigned for the opening of the Constituent Assembly, November 28th, all the Socialist-Revolutionist deputies who were elected had come to Petrograd. You know that neither violence of a usurping power nor arrests of our comrades, by force of arms which were opposed to us at the Taurida Palace, could prevent us from assembling and fulfilling our duty.
But the civil war which has spread throughout the country retarded the election to the Constituent Assembly and the number of deputies elected was insufficient.