Who was the Writer politician and poet first to write in Italian language of people?

The first writer, politician, and poet to write in the Italian language of the people is considered to be Francesco Petrarca, also known as Petrarch.

While others had written in vernacular Italian before him, Petrarca's work marked a significant shift towards the use of Italian as a literary language. He is known for his sonnets, which celebrated love and beauty, as well as for his letters and epics. His work helped to establish Italian as a major literary language and contributed to the development of the Italian Renaissance.

However, it's important to note that the Italian language was still evolving during Petrarch's time. He wrote in a Tuscan dialect, which was not the standard Italian language of today.