Pro-Europe centrist Macron, 39, was elected on Sunday after promising a "revolution" that would bring in fresh faces into France's stale political life and end the pattern of power alternating between traditional parties.
His newly renamed grassroots movement, "Republique en Marche" (Republic on the Move), which was founded only 13 months ago, will finally reveal the vast majority of the 577 candidates who will stand in parliamentary elections in June.
Macron has promised that half will be complete newcomers, meaning a diverse range of figures from business, civil service, local activism and academia are set to make their first foray into politics. Half of all candidates will be women.
"The second act in the redrawing of our political life will be the building of a parliamentary majority in the elections in June," secretary general of the movement, Richard Ferrand, told reporters on Monday.
The nomination process is a careful balancing act for Macron and represents major risks for his presidency, which will begin formally on Sunday when he takes over from outgoing Socialist Francois Hollande.
Without his own parliamentary majority, he will find it hard to push through his planned reforms of the labour market, pensions, unemployment benefits or education.
Many of his newcomers, which have been approved by a nomination committee, will be up against seasoned politicians with long careers and local networks of activists and supporters.
And there is also the risk of scandal if anyone with a chequered history slips through the vetting process of the roughly 15,000 applications sent on line.
Only 14 candidates have been revealed so far.
Among the approximately 450 candidates set to be announced on Thursday will be a number of familiar political faces from the Socialist party and from the centrist party Modem, headed by Macron ally Francois Bayrou.
The president-elect is left-leaning -- a one-time Socialist party member -- and was a senior advisor to Hollande and an economy minister in his government 2014-2016.
No-one who planned to stand for the rightwing Republicans party has defected, party secretary general Bernard Accoyer said on Thursday despite efforts to recruit them.
As well as deciding on the crucial figure of his first prime minister -- which will send a powerful signal about his intentions -- Macron has also had to grapple this week with the case of a problematic former colleague.
Ex-prime minister Manuel Valls, a one-time centrist ally who lobbied for Macron to join the government in 2014, has declared his desire to stand for Macron's party in the parliamentary elections.
But relations between Valls and Macron deteriorated badly during their time in government and the heavy-hitting Spanish-born ex-leader is disliked by many Republique en Marche insiders.
He was abruptly told he had to apply online and should not assume he will be accepted.
"The idea, whatever people say, is not to humiliate candidates or treat them brutally," one En Marche insider told AFP on condition of anonymity.
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