ardent, enthusiastic, firm, great, outspoken, powerful, staunch, strong
She''s a staunch advocate of free trade.

chief, leading, main, principal

~ for
He is one of the leading advocates for a more modern style of worship.

~ of
an advocate of pacifism

defence

seriously, strongly
Heart specialists strongly advocate low-cholesterol diets.

be widely advocated
These policies have been widely advocated.