MLSTP–PSD holds a commanding lead in the São Tomé and Príncipe parliamentary election market ahead of the 27 September vote because the party backed President Carlos Vila Nova’s first-round re-election in July, securing over 55% of the vote and demonstrating effective coalition-building after the 2025 split with ADI. The proportional representation system and MLSTP’s organizational strength across districts position it to secure the largest share of the 55 seats, with traders viewing the recent presidential result and incumbent alignment as decisive momentum. ADI, currently holding the most seats but divided by the prime ministerial transition, and smaller parties face structural barriers in a fragmented field. Late shifts could occur if turnout surges among diaspora or opposition voters or if last-minute campaign developments alter perceptions of economic performance, though the current trader consensus reflects the limited time and resources for challengers to close the gap before polls close.