Final answer:
Warren Harding is the president who commonly misspoke and campaigned on the promise to return the nation to 'normalcy,' a term he made popular during his 1920 presidential campaign. Option C.
Step-by-step explanation:
The president who often misspoke and promised to "bring the nation back to normalcy," with "normalcy" being a misused and mispronounced word, was Warren Harding. His campaign for presidency in 1920 centered around this concept of returning to a simpler past, or 'normalcy,' following the end of World War I.
This term, although often mistakenly referred to as a malapropism, became a catchphrase of Harding's presidency and underscored his policies that focused on pro-business stances and a decreased role for the government in both domestic and international affairs.
Harding's administration also faced considerable challenges, including significant scandals. Nonetheless, his promise of a return to 'normalcy' resonated with a populace weary from war and pandemic, resulting in a landslide victory in the presidential election. Option C.