Along with some 20 other people including André D'Allemagne and Jacques Bellemare, he was a founding member of the Rassemblement pour l'indépendance nationale (RIN).
Chaput claims to have become a partisan of the independence of Quebec as part of the Groupe Reboul while preparing for a public debate on the subject of separatism.
He and his team member Jacques Boulay had to argue for separatism in a debating contest against two comrades, Roland Dompierre[B 2] and Réal Denis.
His team lost the debate held on December 10, 1937, but the readings he did to learn about the subject (Séparatisme, doctrine constructive by Dostaler O'Leary, old issues of the paper La Nation by Paul Bouchard, history books on the Patriots of the 19th century) convinced him of the merit of the idea in itself.
He considered that he and the other pioneers of the contemporary movement for the independence of Quebec did nothing but update an idea that goes back to the British conquest of French Canada in 1760.
[A 5] He had been working at the Eddy paper manufacture since May 1939 when the National Research Council (NRC) of Canada granted him a job interview in the month of December of the same year.
He was hired as chemistry laboratory aid to doctor Richard Helmuth Fred Manske for a salary of $70 CAD per month.
After suffering from pleurisy, the doctor ordered his wife to leave the overheated rooms where the Chaput family was living and take some rest.
Madeleine packed her things and returned to Marcel's parents in Hull, while he rented a room in Montreal in the neighbourhood of McGill.
[A 8] This study would have helped General Jean-Victor Allard to convince the federal government to create francophone units in the Canadian Army.
Barbeau invited Chaput to give a short speech in the Saint-Stanislas room of Montréal on September 13, 1959 as part of a soirée organized to commemorate the 200th anniversary of the Battle of the Plains of Abraham.
In response to Chaput's initiative, Pierre Vigeant, editorialist at Le Devoir and grand chancelier of the OJC, created a study committee on the question of independence of Quebec.
As secretary to the commission, Chaput wrote the final report which concluded that French Canadians enjoy the right to self-determination and that members of the OJC should feel free to support independence if such was their political conviction.
[A 9] On September 10, 1960, he took part with 20 other people to the foundation of the Rassemblement pour l'indépendance nationale (RIN) which took place at the Auberge Le Châtelet in Morin Heights in the Laurentides.
[A 7] After having participated in the organizing of a parade for independence in the streets of Montreal which took place on February 11, 1961, he gave a conference entitled Le Canada français à l'heure de la décision[B 6] as part of a public meeting held at the Gesù on April 4, 1961, during a Stanley Cup semi-final.
[A 10][B 8] Chaput's increasingly active involvement in public affairs did not fail to grab the attention of his employer, the federal government in Ottawa.
[A 11] The Parliament of Canada took interest in his case again after some French-speaking MPs received invitations to attend a public meeting of the RIN announced for May 30, 1961 at the École normale de Hull.
The day of the event, Chaput was called in the office of doctor Keyston, vice-president of the Defence Research Board, and was threatened with firing if he gave his talk.
Under his presidency, the RIN gave itself an emblem, founded the journal L'indépendance and created a political committee which prepared the programme adopted by members during the annual congress of October 1962.
When during fall Jean Lesage announced there would be general elections on November 14, Chaput thought the time right to present himself as candidate for the RIN in the electoral district of Bourget.
[A 14] On Saturday October 20, during a congress held in the gymnasium of the Collège Mont-Saint-Louis, Guy Pouliot succeeded Chaput in the presidency of the RIN.
On May 7, Raymond Barbeau announced in a press conference that he decided to dissolve the Alliance laurentienne to unite the strength of its members to that of the PRQ.
Since his resignation as a civil servant in December 1961, he had been living on his own savings and an insufficient public service pension to meet the needs of his wife and children.
At the end of the March 1964, his friend Jacques Lamarche suggested he apply for a teaching position with the Fédération des collèges classiques.
Lamarche therefore invited him to join him at the journal Le Laissez Passer published by the Conseil d'expansion économique (CEE), at the time presided by Sarto Marchand and directed by Bernard Tessier.
[A 17] A sympathizer of the RIN, José Leroux, principal of the private Collège Valéry, offered him a position as teacher of biology and history.
On February 5, 1965, in a moment of discouragement, he addressed a public letter to the media to lament the fate Quebec society reserved to those who advocated independence.
[citation needed] On December 11, 1969, he took part in the "manif anti-manif"[B 9] organized by poet Gaston Miron to denounce the municipal regulation forbidding public demonstrations in the streets of Montreal.
[citation needed] He held a political column entitled "La comédie canadienne" in the weekly Point de mire during the year 1971.
[B 11] During that period, he published the book L'école de la santé and in collaboration with chemist Tony Le Sauteur, Dossier pollution.