Pope Pius XI
Quadragesimo Anno §27
Quadragesimo Anno: On Reconstruction of the Social Order
27 And while the principles of Liberalism were tottering, which had long prevented effective action by those governing the State, the Encyclical On the Condition of Workers in truth impelled peoples themselves to promote a social policy on truer grounds and with greater intensity, and so strongly encouraged good Catholics to furnish valuable help to heads of States in this field that they often stood forth as illustrious champions of this new policy even in legislatures. Sacred ministers of the Church, thoroughly imbued with Leo's teaching, have, in fact, often proposed to the votes of the peoples' representatives the very social legislation that has been enacted in recent years and have resolutely demanded and promoted its enforcement.
Source: Quadragesimo Anno (Vatican.va)