Spencer rarely delved into his own life for subject matter. In The Evangelist, however, he may have summoned a childhood memory. His father was a Swedenborgian clergyman who often changed his parish, and this painting reflects the nomadic life of a clergyman who preaches from makeshift platforms.
In the course of his career, Spencer progressively deemphasized architecture and stressed the figure. In the vertical tripartite division of The Evangelist, the platform and its inhabitants occupy the central panel and face the viewer, thus limiting perspective.
Spencer's technique changed little during the 1910s, varying only in the degree of impasto. As seen in The Evangelist, he blocked in areas of color that he then scraped back to reveal the weave of the canvas. The second layer of paint was applied in short choppy strokes to create texture. The color is muted and somber, befitting the subject. Phillips particularly responded to Spencer's use of color and line in The Evangelist, as when he observed that "...the gaunt unlovely platform permits handsome accents of black silvered in sunlight and contrasts delightfully with the pinks, grays, and whites of the village crowd and with the lyrical light of late afternoon on the banks of the Delaware." Exhibited twice as often as any other work by Spencer, The Evangelist remained one of Phillips's favorite paintings. In A Collection in the Making, he considered it to be "a masterpiece of American genre."