Benoît Martin, a leading union official with the leftist CGT, which is leading the charge on the strike, framed it as all about Mr. Macron himself. “It expresses a sort of resistance to Macron’s power,” Mr. Martin said.

True, Mr. Macron’s plans by themselves spark fear in a nervous France demanding more security, not less. The current pension system is one of the world’s most protective, for all its flaws. Many French are asking why a plan of uncertain contours and outcomes should be substituted for it.

But Mr. Macron argues that the current byzantine system is both unaffordable and unfair. It could be headed for a deficit of about $19 billion, and its disparities allow workers in some sectors to retire years ahead of others.

While Mr. Macron is not proposing to spend less on pensions or to make people retire later, he aims to simplify the system, raising fears that he will reshuffle its winners and losers.

The pension plan is not the first of Mr. Macron’s reforms to face resistance. His changes to the status of the country’s railway workers and revamping of France’s voluminous labor code met similarly fierce protests on the street.

Some of those changes made it easier to hire and fire workers and have helped nudge down a stubborn unemployment rate that once hovered around 10 percent to about 8.4 percent this year. Yet for many French the perceived benefits don’t outweigh the feeling of insecurity they have introduced.

Beyond that there is striking disaffection with the way Mr. Macron goes about presenting himself and his ideas.