Democrats' divisions test Biden's front-runner strength

DETROIT — The ideological divisions gripping the Democratic Party intensified on Wednesday as presidential candidates waged an acrimonious battle over health care, immigration and race that tested the strength of early front-runner Joe Biden's candidacy.The former vice president was repeatedly forced to defend his decades-old political record against pointed attacks from his younger, diverse rivals, who charged that Biden's eight-year relationship with President Barack Obama was not reason