As UDC member and deputy-mayor of Crespano del Grappa, his hometown, he came to regional and national prominence for his request that municipalities would retain for themselves 20% of personal income tax.
[1][5] Guadagnini was soon chosen as the party's candidate for President of the Province of Treviso in the 2011 provincial election.
In October 2011, during a party congress in Vicenza, he was elected secretary of VS, succeeding to Lodovico Pizzati.
[8][9] Having led the party into the Independence We Veneto (INV) coalition (in support of Luca Zaia's re-election for President) and stood as a candidate in the 2015 regional election and was elected to the Regional Council of Veneto from the provincial constituency of Vicenza.
[10] Soon after being installed, Guadagnini, who was also appointed Secretary of the Council, formed a pro-independence "inter-group", which was joined from the start by Stefano Valdegamberi, a former fellow UDC member who had been re-elected councillor in Zaia's personal list, and Massimiliano Barison of Forza Italia.