Ryan has served as the DuPage County state's attorney and as Illinois attorney general.
Birkett praised Ryan, saying he always put the public interest first. He said Ryan is tested, and when he looks at a problem, he finds a creative solution.
"These are tough times in Illinois. In politics and in leadership, guts is everything. Jim Ryan has the guts that it takes to truly lead in this state," Birkett said.
"People are hungry for authentic leadership. They're hungry for transformational change," said Ryan.
Ryan is competing with a crowded field of Republican candidates. It includes Adam Andrzejewski, Bill Brady, Kirk Dillard, Andy McKenna and Dan Proft.