Macron led on Sunday the first round of voting for president, with projections based on partial results showing him polling 23-24 percent to Le Pen's 21.6-23 percent.
The two go through to a second round on May 7. Nine other candidates were eliminated.
Among those who endorsed Macron, directly or indirectly, were:
Conservative candidate Francois Fillon
In a concession speech, Republicans party nominee Francois Fillon called for a vote for Macron. Accusing Le Pen's National Front of being "known for its violence and extremism", the former prime minister said: "There is no other choice but to vote against the far right."
Socialist candidate Benoit Hamon
The Socialist candidate shown trailing a distant fifth called on his supporters to give Le Pen the "strongest possible beating" by voting for Macron.
While insisting that Macron "does not belong to the left" Hamon said he made "a clear distinction between a political adversary and an enemy of the Republic" -- referring to Macron and Le Pen respectively.
French President Francois Hollande
Hollande called his former protege Macron, who served as his economy minister from 2014 to 2016, to congratulate him on qualifying for the runoff.
Presidential aides said the outgoing Socialist leader, who decided against seeking re-election in the face of dire approval ratings, would soon explicitly endorse the centrist.
Cazeneuve called on the French to support Macron in order "to beat the National Front and its dreadful programme of regression for France and division among the French.
Former Prime Minister Alain Juppe
The former prime minister who lost the Republicans nomination to Fillon last year said he would vote "without hesitation" for Macron against the far-right, "which would lead France to disaster".
Some leftist also-rans shied away from backing the pro-business Macron.
The hard-left firebrand, whom projections showed tied with Fillon in third, refused to concede defeat until the final official results were announced and said it was up to his supporters to decide how to vote in the runoff.
The Ford factory worker, who ran for the New Anticapitalist Party, blamed the rise of Le Pen on the "austerity and security policies" of the Socialist government that Macron quit last year to run for president.
"To drive back this threat for good, there is no other solution but to win back control of the street against the far right but also against all those like Macron who have, or want to implement anti-social measures," Poutou said.
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