Joe Biden’s glide path to the Democratic presidential nomination begins Saturday as South Carolina, the state that rescued his struggling campaign four years ago, kicks off the party’s official primary season. Biden stands as the overwhelming favorite to win the South Carolina primary against comparatively weak opposition: U.S. Rep. Dean Phillips of Minnesota and Marianne Williamson, an author who ran unsuccessfully in 2020. Early voting in the state began on Jan. 22. Polls close 7 p.m. ET on Saturday. Apart from the fundraising advantages that flow from incumbency, Biden is the favorite of South Carolina’s Democratic establishment, notably Rep. James...