This is the 980th most frequent Italian word.
schlein
"Schlein" is not an Italian word; it is a surname.
In this sentence, 'Schlein' refers to a proper noun, the name of a prominent individual.
Schlein è una figura politica di rilievo in Italia.
Schlein is a prominent political figure in Italy.
Here, 'Schlein' is used possessively, to specify the program associated with an individual called Schlein.
Il programma di Schlein promette molte riforme.
Schlein's program promises many reforms.
This sentence uses 'Schlein' to attribute an idea to the individual named Schlein.