BRUSSELS — Spanish center-right lawmakers have quietly pulled back from their once-robust public support for the EU–Mercosur trade deal, sending jitters through the European People’s Party as backers warn the agreement could now be in serious trouble. The mammoth trade deal, which has been in the making for 25 years, will be formally sealed when European Commission President Ursula von der Leyen flies to Paraguay on Saturday to sign it. But the accord still requires a formal green light from