As
Quakers, Lewelling's family were opposed to slavery, and his brothers Henderson, John, and William were active
abolitionists in Iowa before Henderson left for Oregon. Although Seth Lewelling isn't known to have engaged in abolitionist work himself, the names he gave to his cherries reflect his anti-slavery views. He did not become active in politics, however, until after marrying his second wife, Sophronia Vaughn Lewelling, in 1885. With Henderson Luelling's son Alfred, the couple became leaders first in the
Farmers'Alliance and subsequently in the
Populist Party. Seth and Sophronia played an important role in Oregon's initiative and referendum movement.
William S. U'Ren, a young lawyer recovering from tuberculosis, was introduced to the Lewellings in 1892.They invited him to stay on the farm, and Seth later hired him as manager of the nursery. U'Ren found his life's calling through the Farmers' Alliance meetings in the Lewelling home. With financial support from Seth and campaign help from Sophronia, Alfred, and other Milwaukie residents, U'Ren was eventually able to get Oregon's initiative and referendum system passed by popular vote. U'Ren went on to achieve other populist reforms in the state.{{cite book | title=The Life and Death of Democracy == Death ==