PARIS — The reckoning for France’s longest-ever transport strike is not yet in, even as the action itself is losing steam. On Monday, the national rail company said traffic was “near normal” on much of its network, although the strike is not officially over.

But when the winners and losers are tallied, one man previously consigned to the political dead will have to be counted among the living: Philippe Martinez, the combative head of the country’s most militant union.

Behind his giant mustache, Mr. Martinez, an ex-communist who heads France’s oldest union, the General Confederation of Workers, or C.G.T., has become the public face of the strike, which he has used to revive a moribund union movement that was shedding members.

He has risen as the counterpoint to President Emmanuel Macron and to his business-friendly vision for France. He is omnipresent on television and radio. His giant image plasters the walls of the city’s news kiosks. He is visible at the head of weeks of marches through Paris. He pops up at early-morning pep rallies to keep the strikers mobilized.