detentar

To hold a position, title, or power illegitimately or without proper right — the RAE sense is specifically negative: retaining office or authority that isn't rightfully one's own. It shows up constantly in journalism describing dictators or officials clinging to power, but is very frequently misused.

• El dictador detentó el poder durante casi tres décadas. — The dictator held power illegitimately for nearly three decades.
• La oposición acusó al alcalde de detentar el cargo tras perder las elecciones. — The opposition accused the mayor of clinging to the post after losing the election.
• Los historiadores describen cómo el general detentaba el mando sin ningún mandato legal. — Historians describe how the general held command with no legal mandate at all.

Using detentar for anyone who simply holds a legitimately earned position — Spanish style guides are explicit that "el presidente detenta el poder" is a common but incorrect usage; for a legitimately held office, use ejercer, ocupar, or ostentar instead.

Often confused with ostentar.