How many Supreme Court justices will the President confirm?

**Stage 1 — Blind analysis (ignore market prices):**

Over a four-year presidential term the modal historical outcome is usually one or two Supreme Court vacancies; zero or three+ do happen but are less common. Key structural facts drive my independent estimate: (a) there are nine lifetime-tenured justices, several of whom are elderly enough that at least one retirement or death during a four-year span is reasonably probable; (b) modern strategic retirements mean incumbents often time departures to a President of a favorable party, which concentrates departures into windows that produce 0–2 vacancies per term; (c) when a single vacancy exists, Senate confirmation rates for Supreme Court nominees in recent decades have been high unless the Senate and President are in deep partisan opposition or the nominee is extraordinarily controversial.

I combine these qualitative drivers into a simple conceptual model: probability that exactly one vacancy occurs during the term times the probability the nominee is confirmed (plus small adjustments for scenarios where multiple vacancies net out to exactly one confirmed seat because another nomination is rejected or withdrawn). Roughly: probability of exactly one vacancy alone I estimate at ~0.55 (historical frequency and age structure). Given one vacancy, confirmation probability conditional on the political environment I estimate ~0.85 (courts nominees are usually confirmed if the majority in the Senate aligns or if opposition chooses not to filibuster). Multiplying yields ~0.47; add adjustments for cases where multiple vacancies happen but only one confirmation occurs (withdrawals, blocks) pushes me to ~0.52. That is my independent probability that the President will end the term having secured exactly one confirmation.

**Stage 2 — Market calibration (compare to current market prices and explain differences):**

The market prices put the single-confirmation outcome at 47% (market slightly lower than my independent 52%). The market also assigns a larger share to two confirmations (31%) and to zero confirmations (22%) than my model. Possible reasons markets differ: market participants may be overweighting (a) the historical multi-vacancy average (some bettors expect two vacancies as the baseline), (b) political uncertainty over Senate control and confirmation fights (raising the perceived chance of zero confirmed seats), or (c) event hedging and liquidity flows that favor distributing probability across adjacent outcomes. Conversely, my model places more weight on the single-vacancy, high-confirmation dynamic because strategic retirements and the track record of eventual confirmations for mainstream nominees make “one confirmed replacement” the single most probable path.

Where the market might be mispriced: if several bettors are extrapolating a long-run average vacancies-per-term without properly accounting for *strategic retirements* (which compress departures into predictable windows) or if bettors overweight the possibility of a confirmation failure based on partisan rhetoric rather than institutional incentives (Senators typically prefer having a confirmed justice even under partisan pressure). That would make the market understate the single-confirmation probability and overstate the probability of 0 or 2. However, the market may correctly be pricing nontrivial tails — multiple retirements or a successful blockade — which my central estimate discounts but still accounts for.

Bottom line: my independent assessment (52%) is modestly higher than the market (47%) because I view a single vacancy plus a likely confirmation as the single most probable path, while the market spreads more probability to the adjacent outcomes reflecting political uncertainty and risk aversion among traders.