The ruling party of Russian Prime Minister Vladimir Putin opens a two-day congress today.
The United Russia party is due to discuss and pick candidates for parliamentary elections to be held in December.
United Russia holds 315 of the 450 seats in the State Duma, the lower house of parliament.
Analysts say results from the parliamentary poll could help to decide who will run for president from the party next March: Putin or his protege, President Dmitry Medvedev.
Putin, who served as president the maximum two straight terms from 2000-2008, is free to run again and has said he may do so.
Analysts say a poor result in December could signal that Putin's conservative policy is losing support and prompt him to give the younger and more liberal Medvedev a second chance.
A VTsIOM opinion poll in July had United Russia narrowly losing its two-thirds majority, securing 291 of 450 seats in the lower house.
Both Putin and Medvedev will address the congress in Moscow on September 24.
compiled from agency reports