As usual, the man getting all the attention in Spain is a sportsman. But this time it is not Nadal, or Iniesta. His name is Luis Bárcenas. He is a man of high places, both as an mountaineer and as an accountant – an activity you may regard as a little less glamorous. Not in this case. Bárcenas may have climbed Everest, but it is actually his accounting practices as the former treasurer of the ruling People's party (PP) that makes for gripping reading. Now his most avid reader is a judge of the national court in Madrid, and if what Bárcenas has been telling him is true, it has the potential to bring down the government and destroy the PP.

Or maybe not.

What Bárcenas claims is that the People's party has been running a slush fund for nearly two decades. According to him, the party has been routinely receiving large illegal donations from businesspeople, then dividing them among party leaders as payments on the side. This would include the current prime minister, Mariano Rajoy. On Monday morning, Bárcenas provided the judge with what he says are the secret accounting ledgers of the party for the past two decades. There, in his neat handwriting, familiar names pop up frequently, with fat figures on the side. Everybody who is anybody is there. It's almost like the Wikipedia of Spanish conservatism. And the suspicion that donors might have expected political favours or contracts in exchange for their money is not entirely absurd – though still unproven.

Bárcenas is not hiding his main motive for doing this: revenge. He is in jail, pending an investigation on his own unexplained fortune held in Swiss accounts. He expected his case to be dismissed after his party's victory, but all he allegedly got was short text messages from the prime minister telling him to "remain strong".

Now Bárcenas has lost patience with Rajoy. He is certainly not the first in Spain, but he might well be the one whose anger matters most to the prime minister. Or does it?

Because the most extraordinary thing about this scandal is not its reach or its gravity, but the strange way in which it is being addressed by Rajoy. Or not addressed, actually. The prime minister simply refuses to talk about it. He has mastered the art of never mentioning the treasurer's name in public, exhausting every possible circumlocution. Time and again he repeats the same flat, mysterious denials; and this only when he bothers to answer at all. He shuns parliament, he rarely gives interviews, even to friendly media, and he runs away from reporters. For some time he decided to address the press by means of a plasma TV to avoid questions. It was definitively weird.

Nobody expects him to quit his job in a country in which resignations over ethical issues are almost unheard of, but even his voters are demanding an explanation. They're getting none from Rajoy. Bárcenas should consider himself lucky, at least he gets texts from him.

But here's the thing that few dare to admit: it works. Spin doctors would tell you that when you're under attack you need to explain yourself, that silence is an admission of guilt. Rajoy is proving all of them wrong. His statements are so short and empty of information that they don't leave any room for analysis, and his refusal to show himself in public is beginning to imbue him with an aura of invisibility. He is rewriting the book on damage control, replacing it with another one with blank pages.

How long this can go on is impossible to say. It's an experiment. What we are seeing is that Spain still lacks a strong civil society. Years of quid pro quo reforms have made politicians invulnerable to public scrutiny and, as long as he keeps his party united behind him, Rajoy's absolute majority in parliament shields him not just from resigning, but even from responding. Only an indictment would be a game changer, and that is what Bárcenas has set out to achieve in what promises to be the ultimate political combat between anger and silence.

That's the sorry state of Spanish politics: naked personal revenge seems to have become the only available substitute for accountability.