Polymarket account stakes $846,000 on Republicans losing House control

A Polymarket account using the name “rdba” put $846,000 behind Democrats winning the House in the Nov. 3 midterms, buying 900,000 contracts that paid out if Republicans failed to retain control.

The Oct. 30 purchase was made at 94 cents per “No” share in Polymarket’s Republican House-control market. If Democrats won, the original position would return $900,000, for a gross profit of $54,000, or about 6.4%. Gaming America described it as the largest single wager on the midterms across Polymarket and Kalshi, though RG said it had not independently verified that ranking.

Most of the other side of the transaction was taken by an account called BreakTheBank, which bought about 899,900 Republican “Yes” shares at 6 cents. That position cost roughly $54,000 and would pay about $900,000 if Republicans held the House.

The trade was placed while both exchanges put the Republican chance at roughly 6.5%. Polymarket was already strongly favouring Democrats, who traded at 93% on Oct. 30, according to Goldsky’s market data. By about 12:10 p.m. Eastern time on Sunday, Polymarket put the Democratic price at 94.5%, against 5.5% for Republicans, with $35.7 million traded in its House-control market. Kalshi’s corresponding contracts last traded at 93.6 cents for Democrats and 6.5 cents for Republicans.

rdba subsequently converted the 900,000 contracts into Democratic-control “Yes” shares, which settle on the same result. Beginning Sunday, the account sold part of that position at roughly 95 cents. By 12:12 p.m., it had sold about 158,500 shares in 53 transactions for about $150,600, leaving around 741,500 Democratic shares.

After the partial sale, a Democratic House victory would leave the trader about $46,000 ahead of the original stake, excluding fees. A Republican win would produce a loss of about $695,000. Polymarket’s public leaderboard listed rdba with roughly $435,000 in lifetime profit on $47.2 million in trading volume.

RG reported that much of the money appeared to have come from a $679,650 redemption on Oct. 25 after a wager against Flávio Bolsonaro in Brazil’s presidential election. Polymarket International identifies accounts by wallet address and username rather than a verified public identity, so the person or group behind rdba is not identified in the market data.