Harmony's support in June grew by 1.8 percentage points on May to reach 21 percent.
Other parties to see an uptick in their ratings were the liberal-oriented "For Development/For!" alliance which saw its rating grow 1.7%, the New Conservative Party, which climbed by 1.6% and KPV LV, which picked up by 1.4%.
For Development/For! clocked 4.7 percent support overall, followed by KPV LV with 4.4 percent, and the New Conservative Party with 4.0 percent.
All three are relatively new, smaller parties who will see the data as improving their chances of winning seats in Saeima, which has a 5% threshold.
Meanwhile the Greens and Farmers Union of Prime Minister Māris Kučinskis remained the second most popular party in June, with 14.4 percent support, down 0.2 percentage points on the previous month, while support for the right-of-center National Alliance was at 6.1 percent, down by 0.9 percentage points.
An attempt to improve the fortunes of the Unity party be rebranding it New Unity appears to have been ineffective as it saw a substantial reduction in voter support in June, down one percentage point to 2.7 percent.
After New Unity, the next most popular party is the Latvian Regional Alliance with 1.7 percent, For Latvia From the Heart with 1.5 percent, the Latvian Russian Union with 1.2 percent, and the Progressives with 1.1 percent.
As always, those figures, based on a sample of more than 1,000 voters, come with a huge caveat: 23.7 percent of voters are undecided on which party they will vote for, while 13.2 percent do not plan to vote at all.