Before the April polls he regularly lobbed insults at his main rival, socialist Prime Minister Pedro Sanchez, but last month Casado said he was willing to form pacts with “all constitutional parties, including the Socialists”, although he ruled out a grand coalition.
“Today Casado is a much more mature politician,” said Euprepio Padula, a leadership coach and political adviser who has worked with several Spanish politicians.
The 38-year-old steered the PP further to the right after taking the helm of the party in July 2018.
He had to win a hard-fought primary, that followed the ouster of former prime minister Mariano Rajoy by a vote of no-confidence.
Casado highlighted his opposition to abortion and euthanasia in a bid to stop votes haemorrhaging in the April election to the far-right Vox party, which burst on the scene last year.
Close to another former Spanish premier, the combative Jose Maria Aznar, Casado accused Sanchez of cosying up to Catalan separatists and Basque nationalists to prop up his minority government.
He caused a stir in February when in a single speech he lobbed more than 20 insults at Sanchez, calling him “the biggest traitor in Spain's democratic history”, a “compulsive liar”, “disloyal”, “egotist”, “mediocre” and “a disaster for the future of Spain”.
The verbal onslaught contrasted sharply with his normal friendly demeanour and it appears to have turned off voters.
The PP's worst election result, winning just 66 seats in April — less than half its total in the outgoing parliament — was “very bad”, Casado admitted.
'Learned the lesson'
He re-emerged after the summer break sporting a new look — a full beard much like the one used by his predecessor Rajoy — and a more restrained tone which he has kept in the lead up to Sunday's repeat general election.
Padula said the PP leader had “learned the lesson” of the April debacle.
“He has adopted a much more moderate role, much more that of a statesman,” added Padula who regularly appears on television to analyse politicians.
Casado has appealed for centre-right voters to back the PP and unseat Sanchez, essentially an appeal to supporters of Vox and the centre-right Ciudadanos party.
“Spaniards who don't want Sanchez to stay on can only make this happen with the PP,” he said in an interview published Sunday in centre-right daily El Mundo.
His criticisms of Sanchez have largely avoided name-calling this time around and he has focused instead on the premier's handling of Catalonia's separatist drive.
“You don't believe in the Spanish nation,” Casado told Sanchez during a live TV debate on Monday, accusing him of going easy on the Catalan separatists.
Polls suggest the new tone is paying off, with the PP set to win 91 seats. The Socialists are tipped to once again take the most seats but fall short of a majority, according to a survey published Sunday in El Pais.
Casado is married to Isabel Torres, a school psychologist, and they have two children — Paloma and Pablito.
When he was picked to head up the PP, beating the more moderate Soraya Saenz de Santamaria who had been Rajoy's right-hand woman, Casado promised “regeneration” in a party plagued by corruption scandals.
However, he was soon involved in a scandal as well, admitting he did not attend lectures to obtain a Masters in regional law, and prompting accusations the academic honour was a “gift”.
The Supreme Court eventually dropped the case.