In October 1918, United States President Woodrow Wilson's Fourteen Points were published in the German press. While in his native village of Olpret, Voevod read about the Wilsonian principles in a newspaper from Munich, which made him realize that instead of demanding the federalization of Austria-Hungary, the only valid alternative was to push towards the union with the Romanian Kingdom. He drafted quickly a proposal in that respect and went to his good friend Iuliu Hossu in Gherla to seek his advice. Pondering over the words in the draft, they decided to replace the most radical proposal with the following generic statement: "Starting now, whatever the Great Powers will decide, the Romanian nation from Hungary and Transylvania is determined to rather perish than to endure slavery and subjugation any further". On 18 October 1918, Vaida-Voevod presented this proposal in the Hungarian Diet, asking for the right to self-determination of the Romanians in Hungary. He began his discourse in a dull tone, then he suddenly read the declaration of self-determination, to the shock of his fellow deputies, who started to throw objects at him. Having prepared his exit in advance, Vaida-Voevod narrowly escaped lynching by leaving quickly through a back door of the Parliament building and hiding in a workers' neighborhood in Budapest, where many ethnic Romanians lived. In December 1918, after the Aster Revolution when Hungary had become a republic, Vaida-Voevod was elected in the Alba Iulia National Assembly that proclaimed the union with Romania, and was, alongside Vasile Goldiș, Iuliu Hossu, and Miron Cristea, a member of the Transylvanian group of envoys that presented the decision to King Ferdinand I in Bucharest.
In Romania
Vaida-Voevod joined the Romanian delegation to the Paris Peace Conference of 1919, and was one of its most prominent members throughout the negotiations, as an organizer of press campaigns. During the conference, he joined the MasonicGrand Orient de France in order to secure a more advantageous position for his country.
First Term as Prime Minister
The elections of November 1919 were successful for his party, and he replaced the National Liberal Ion I. C. Brătianu as Prime Minister and Nicolae Mișu as Foreign Minister. He secured the demarcation lines by ordering Romanian troops to fight off the Hungarian Soviet Republic. However, his radical approach toward the land reforms made King Ferdinand dissolve his government in March 1920, to be replaced by one formed by General Alexandru Averescu's People's Party. Vaida-Voevod's party emerged as the National Peasants' Party in 1926, and he served as its leader. He also served twice as Interior Minister.
Second and Third Cabinet
Vaida-Voevod's second cabinet existed from 11 August until 17 October 1932; he resigned and was succeeded by Iuliu Maniu. After Maniu resigned as Prime Minister in January 1933, Vaida-Voevod returned as Prime Minister. "Vaida and his supporters, who formed the National Peasants' Party's right wing, were acting more like Liberals than Peasantists. They crushed strikes by oil workers in Ploiești and by railway workers in Bucharest in February 1933, dissolved Communist Party front organizations and all other 'anti-state' organizations, and proclaimed martial law in a number of cities." Nonetheless, the problems posed by his new cabinets – the Legionary Movement's intimidation of the political scene, and Vaida-Voevod's own anti-semitism, led to a split between the Prime Minister and his Party. His second government fell because of Armand Călinescu, who was a staunch opponent of the Legionary Movement.