Which party will gain most seats in Russian Parliamentary Election?

The baseline case strongly favors United Russia. It starts from an enormous seat share, dominates the political system, and is operating in an election environment where meaningful national competition is heavily constrained. The recent polling and reporting all point to ER staying far ahead of the nearest rivals, and the main public question is not whether it remains the largest party, but whether it keeps a supermajority or merely remains comfortably in control. That makes it highly likely that ER ends up with the most seats overall, and also a strong contender to post the largest seat gain if the election cycle includes any meaningful redistribution among the regime-aligned parties.

The main complication is that this market is not asking who wins the most seats in total, but who gains the most seats relative to before the election. That opens the door to a narrower path for Yes than a simple plurality market. Because United Russia already has a very large seat base, it may have less room to show a large positive seat gain than a smaller allied party that can add a handful of seats from a low starting point. If the Kremlin chooses to smooth the result by letting one of the smaller loyal parties improve more visibly while keeping ER dominant, United Russia could still finish first in total seats yet fail this specific market if another party records the biggest increase.

Even so, the structure of Russian parliamentary politics still points toward ER being the most likely seat-gainer. Opposition parties are tightly managed, protest votes are limited, and the regime has strong incentives to preserve the image of United Russia as the central governing vehicle. In a controlled setting, seat changes are often engineered rather than left to pure electoral drift, so the authorities can shape outcomes in a way that still leaves ER with the most favorable comparison to the prior Duma if they want that result. The market price implies roughly a three-in-four chance, which looks a bit low if one focuses only on overall dominance, but is reasonable once the seat-gain framing and the possibility of cosmetic redistribution among other loyal parties are taken into account.

The biggest reason not to push the probability higher is the ambiguity around how the final seat allocation will be managed. If ER is intentionally allowed to lose a modest number of seats while another pro-government party is modestly boosted, the market could resolve No even though the political system remains overwhelmingly favorable to United Russia. That risk is real enough to keep this below the mid-80s, but not enough to outweigh the structural advantages that make ER the leading candidate for the largest seat gain.