The Reform Party picked up 4 percentage points in the monthly popularity poll conducted for ERR by TNS Emor, and is now the most popular party in the nation for the first time since November 2012.
If the general elections were held tomorrow. 29 percent of decided voters would cast their vote for the ruling party, according to the poll. The Social Democrats came in second with 27 percent.
The Center Party was third for a second straight month with 24 percent in the poll, increasing its result by two percent.
IRL experienced a significant drop, down to 15 percent, four percentage points less than in April.
As for the parties not represented in Parliament, the Greens got three percent in the poll, the Conservative People's Party received two percent, and the Independence Party one percent.
TNS Emor's Aivar Voog said the Reform Party has gained ground among young voters under 35 years of age and by taking potential votes away from IRL.
The other Emor poll, on European Parliament elections standings, will be released on Saturday.