I found this claim that Hobbes believed he founded political philosophy in multiple reputed places. In this lecture from Yale: 12. The Sovereign State: Hobbes' Leviathan
In Leo Strauss and Joseph Cropsey's book History of Political Philosophy, it says the following Berns says the following in his chapter on Hobbes "Because of what he regarded as his discovery of the true roots of human behavior, his knowledge of human nature, and his scienti way of proceeding, Hobbes believed that he had succeeded where a11 others had failed, that he was the first true political philosopher"
In the Stanford encyclopedia page about hobbes accessible here: Thomas Hobbes: Stanford it says-
" Hobbes thought that he would be renowned as the founder of civil philosophy just as he saw Copernicus as having initiated the “beginning of astronomy”, Galileo as having opened the “gate of natural philosophy universal” with an account of the “nature of motion”, and William Harvey as having first discovered the “science of man’s body” (see the dedicatory epistle to De Corpore; EW I.viii). He asserted that while “Natural Philosophy is… young”, civil philosophy itself is “no older than… [his] own book De Cive” (EW I.ix). "
However, if I navigate to EW I.ix using their bibliography pictured here:[3]bibliography screenshot
This quote cannot be found. Here is the link to the text tagged EW The English works of Thomas Hobbes of Malmesbury