Read previewWhen Vice President Kamala Harris announced that she was running for president on July 21, she changed more than the dynamics of the race — she upended the entire timeline of presidential elections. AdvertisementMichael Sistak, who served as Sen. Mitt Romney's political director in Michigan in 2012, described a presidential campaign as a "long slog through the mud." AdvertisementIn the 1960s, primaries became a fixture of presidential elections and added months to the campaign. The primary system emerged as a decisive force after World War II and solidified its place in the American presidential election process in 1968. "It's a slog from January all the way to the convention," she said about presidential election years.

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