A "forceful advocate" describes someone who strongly and assertively supports a cause or defends a particular viewpoint. They use persuasive and convincing techniques to argue their position. Full definition
A future that sees us step up with confidence to a new, even more internationalist role, where we meet our responsibilities to our friends and allies, champion the international cooperation and partnerships that project our values around the world, and continue to act as one of the strongest and most forceful advocates for business, free markets and free trade anywhere around the globe. (totalpolitics.com)
While it is clear Long Island needs a tunnel, and there hasn't been as forceful an advocate for public works since Franklin Delano Roosevelt, Cuomo is going to need to go beyond engineering reviews, environmental benefits and geological analysis to move forward, or his study will join our study as a thoughtful, expensive, but ultimately academic review of what to build, how and why. (newsday.com)
With help from parents and the many other Americans who trust and support them, they can and should become more forceful advocates — in their local districts, statehouses, and national forums alike — for the kinds of teacher recruitment, preparation, and support that are known to strengthen the profession and yield powerful results for students. (kappanonline.org)