Is poker a game of skill or luck?
Both, and the proportion depends entirely on the timeframe — luck dominates a single hand, skill dominates over a large sample, and the crossover point is the whole subject.
Why luck dominates in the short run. The cards are random. A weaker player can win a hand, a session or a tournament through card distribution alone, and does so regularly. This is essential to the game's economics — if the better player always won, weaker players would stop playing.
Why skill dominates in the long run. Over thousands of hands, card distribution converges and decision quality determines the outcome. Studies of large hand databases consistently find that a small proportion of players are persistently profitable, which random distribution cannot produce.
What the skill actually consists of:
Making decisions with incomplete information, which is the fundamental skill and transfers directly to other domains.
Pot odds and expected value — whether a call is profitable given the price and the chance of winning. This is arithmetic, and is the entry-level skill.
Position, since acting last gives information nobody else has, and is one of the largest single edges.
Hand reading, narrowing an opponent's possible holdings from their actions.
Bet sizing, which conveys and conceals information.
Bankroll management, which is what allows a skilled player to survive variance long enough for skill to express itself. Most losing players are not unskilled at cards; they are unskilled at variance, and stake too high relative to their bankroll.
Emotional regulation — playing badly after losses, called tilt, destroys more results than any technical weakness.
What game theory contributed. Solver software computes near-optimal strategies, and modern high-level play involves studying these and deliberately deviating to exploit opponents who do not play them. This has raised the standard substantially and reduced the edge available.
The legal question follows the same divide. Jurisdictions differ on whether poker is gambling, and the argument turns on whether chance or skill predominates — courts have reached opposite conclusions on essentially the same evidence.