The by-election was called after the Constitutional Council invalidated the election of Lénaïck Adam, candidate of La République En Marche!

As in June 2017, Adam narrowly defeated Davy Rimane, supported by La France Insoumise, in the second round.

[5] The vast constituency, covering an area of 54,013.20 square kilometres (20,854.61 sq mi), includes the communes of Apatou, Awala-Yalimapo, Grand-Santi, Iracoubo, Kourou, Macouria, Mana, Maripasoula, Montsinéry-Tonnegrande, Papaïchton, Saint-Élie, Saint-Laurent-du-Maroni, Saül, and Sinnamary.

[16] Davy Rimane, who narrowly lost to Adam in June 2017, also contested the by-election, this time with the backing of Jean-Luc Mélenchon's La France Insoumise (FI).

As in June, Rimane was backed by Léon Bertrand, who served in the government of Jacques Chirac and is currently mayor of Saint-Laurent-du-Maroni, later twice convicted in two judicial cases.

[15] During the visit, Mélenchon denounced Castaner's travel by helicopter in French Guiana, questioning the financing of the trips; in response, the campaign stated that the trip was properly accounted for, that parts of the constituency are only accessible via air or water, and that the electoral code exempts travel expenses from spending limits.

[26] After a supporter discovered racist graffiti against Riché and posted a video of it on social media,[27] public prosecutor Éric Vaillant announced the opening of an investigation by the authorities in Kourou to locate the person who wrote it.

[31] He ran without the official support of any party, though he previously served as a regional delegate of the UDI youth in French Guiana.

[38] Georges Mignot, a 47-year-old animation assistant, stood for the Popular Republican Union (UPR),[34] replacing Nicolas Miray, who was initially designated as the party's candidate in the constituency.

[26] François Asselineau, president of the UPR, flew to French Guiana in order to campaign in support of Mignot from 25 February to 5 March.

[43] Two debates with four candidates each were broadcast by Guyane 1ère on 21 and 22 February at 20:00 local time, presented by Laurent Marot and Jessy Xavier.