PARIS (Reuters) - French rail unions have launched three months of strike action in a showdown with Emmanuel Macron, but their capacity to sustain it will depend as much on the durability of their and their workers’ finances as on amassing political capital.

Millions of commuters and other travelers suffered a second day of misery on Wednesday as four unions extended a stoppage called over a modernization program that the president has pledged to implement at state-run rail firm SNCF.

For the unions, and in particular the Communist-rooted CGT which counts the railways as one of its key power bases, this may be a last chance to prove they are still a force to be reckoned with in a society that polls suggest is beginning to fall out of love with the more militant side of organized labor.

But running a strike on two days out of every five over three months, as the unions intend, will be a major test for their ability to cushion the blow of their members’ financial losses.

Anasse Kazib, a 31-year-old signalbox operator and member of the Sud Rail union, said the SNCF was deducting a day’s salary for each day he went on strike.

“It’s tough, we have to make sacrifices at home in order to fight this fight,” Kazib told Reuters. “You don’t go out, eat in restaurants. If it drags on, we’ll have problems with the rent, with credit card payments.”

For now, he strikes a defiant tone, determined to press on until “the government pulls its plans” - something it has been equally emphatic in insisting it will not do.

The SNCF, meanwhile, has forecast it will lose 20 million euros ($24.6 million) on each strike day.

While it is too early to put a figure on the full cost of the standoff to the wider economy, a nine-day stoppage in November 2007 over public sector pension reforms - which extended well beyond the rail industry - cut 0.1 percentage points off GDP.

The CGT, Sud Rail and UNSA-Railways depend on donations to mitigate the financial pain for their workers. The CGT is actively encouraging contributions and can ring-fence a chunk of budget if needed, said senior CGT official David Dugue.

The CFDT, France’s largest union in terms of numbers, meanwhile has a substantial war chest available. Its treasurer, Thierry Cadart, said its federations are sitting on a reserve of 126 million euros, raised through a levy on salaries - enough to finance a week-long strike by all its 800,000 members.

Its rail workers were each receiving 7.30 euros for every hour lost to the strike, he said.

Kazib’s union, Sud Rail, said it would prioritize helping its lowest-income workers.

“But it will be a symbolic amount more than anything else,” said Sud Rail secretary Eric Meyer. “It’s the rail workers’ future that is at stake. For now they’re not thinking about their bank accounts.”

($1 = 0.8135 euros)