Kickbacks, fake invoices and Swiss bank accounts: the juicy details of the so-called Gürtel affair -- which allegedly saw PP politicians across the country receive bribes - are well known by Spaniards who have become all too used to corruption in politics.
But this time, Spanish media have billed it as the "trial of the year" as three former party treasurers are among the 37 defendants - including Luis Barcenas, who stashed tens of millions away in Switzerland.
What makes the case all the more intriguing is that the PP itself has been called to the stand for allegedly benefitting from funds obtained illegally by lawmakers.
But unlike the defendants, the party as a whole faces no criminal charges and may merely be asked to pay the money back.
The case has been given the code-name "Gürtel ", the German translation of "belt", or "correa" in Spanish -- the surname of the man who allegedly led the sprawling corruption network.
Francisco Correa, a businessman who liked to be called "Don Vito" in reference to the mob boss played by Marlon Brando in "The Godfather", is accused of having showered PP lawmakers and councillors with bribes between 1999 and 2005.
In exchange, his companies or those of his friends were given contracts for public works or for organising events, such as the 2006 visit of Pope Benedict XVI in the eastern city of Valencia.
Last year, online daily eldiario.es published a confession from Correa, who for more than three years swapped his flashy lifestyle for prison where he was remanded in custody from 2009 to 2012.
He said companies would give him "a commission of 2 to 3 percent" on the value of public works contracts awarded to them, which he would then give to Barcenas, "in cash", after taking his share.
Correa, who was close to former conservative prime minister Jose Maria Aznar, has threatened to spill the beans on "everything he knew."
The case claimed a high-profile victim early on, forcing the resignation of then health minister Ana Mato in 2014.
Her ex-husband Jesus Sepulveda is on the stand for embezzlement of public funds and influence peddling as former mayor of Pozuelo de Alarcon, a town near Madrid, from 2003 to 2009.
His family is alleged to have profited with various gifts, holidays or birthday parties complete with clowns.
Mato herself is accused of benefiting from her ex-husband's offences, though like the PP she does not face criminal charges.
Rato in court next door
The case also claimed another victim in the form of Spain's superstar judge Baltasar Garzon, who had ordered the first detentions in 2009 after a lengthy probe.
In 2012, he was suspended from the judiciary for 11 years after being found guilty of ordering illegal recordings of corruption suspects talking to their lawyers in the Gürtel affair.
The trial that kicks off Tuesday at Spain's National Court just outside Madrid is due to last several months.
Coincidentally, former IMF chief Rodrigo Rato will also be testifying on Tuesday in a separate trial in the same building.
Rato, a former economy minister and fallen star of the PP, is on the stand for allegedly overseeing a "corrupt system" that helped him and other executives misuse millions when he was a Spanish banking boss.
By Laurence Boutreux / AFP