The phrase "leading exponents" refers to people who are considered experts or highly influential in a particular field or subject. They are considered the top figures who have extensive knowledge and expertise in that area. Full definition
, presenting 250 drawings by a wide cross section of well - known contemporary artists, and In Praise of Shadows, featuring shadows, shadow theatres and silhouettes by many leading exponents of that genre. (imma.ie)
While Modernist poetry in English is often viewed as an American phenomenon, with leading exponents including Ezra Pound, T. S. Eliot, Marianne Moore, William Carlos Williams, H.D., and Louis Zukofsky, there were important British Modernist poets, including David Jones, Hugh MacDiarmid, Basil Bunting, and W. H. Auden. (en.wikipedia.org)
Both artists (during the 1930s and 40s, at least) were leading exponents -LSB-...] (artlyst.com)