Reform increased its lead over EKRE from 1 percent to 5 percent in September, polling from Kantar Emor shows.
Emor's recent polling is compared with July as the company did not carry out any research in August.
In July, EKRE was the most popular party with 25 percent support followed by Reform on 23 percent. But the latest polling shows Reform on 27 percent and EKRE on 22 percent.
In September, support Center and Eesti 200 were equal on 16 percent, a fall for Center which had 20 percent in July.
The Social Democratic Party's support fell from 11 percent to 9 percent, Isamaa's increased from 4 percent to 6 percent.
The Greens had 3 percent and TULE 1 percent.
Emor does not include the "cannot say" category in its results to make them comparable to the situation in the Riigikogu elections.
But in September, the share of people that said "cannot say" was 20 percent, compared to 27 percent in the last poll.
Editor: Helen Wright