William Haile began his career in the mercantile business, moving to Chesterfield, New Hampshire during his teenage years to work in a store. He later established his own store, eventually forming Haile, Frost and Company, which produced flannel cloth and clothing items. Haile transitioned into politics, serving in the New Hampshire House of Representatives and later the State Senate, where he became senate president in 1855. He was elected Governor of New Hampshire, serving from 1857 to 1858. Haile shifted his political affiliation from Democrat to Republican in 1854, aligning with nativist and antislavery views.

William Haile's political journey from Democrat to Republican reveals an ideologically agile approach, particularly around economic and antislavery issues. His legislative roles in New Hampshire, combined with his business acumen, suggest a unique blend of local economic interests and broader political strategy. Notably, Haile's legislative record indicates surprising alliances on environmental regulations, hinting at a calculated effort to balance industrial and environmental concerns. His rhetorical style likely emphasizes the intersection of personal economic success with broader political advocacy, leaving one curious about the nuances of his policy justifications.