DETROIT — Hillary Clinton has a clearer path to the Democratic presidential nomination than she ever had in 2008. But she is marching toward November facing the likelihood of an unpredictable opponent — and constrained by well-defined characteristics that have always limited her ability to inspire.

The former first lady calls it her “responsibility gene”; rivals deride it as poll-tested caution. Either way, it leaves Mrs. Clinton trying to hit singles and doubles while her Democratic socialist challenger swings for the fences.

Bernie Sanders advocates tax increases of $15 trillion affecting all income groups; Mrs. Clinton seeks an additional $1 trillion in revenue and would leave the bottom 95 percent of earners alone. He calls for a “Medicare for all” single-payer health care system; Mrs. Clinton aims to build on President Obama’s Affordable Care Act.

He proposes breaking up Wall Street banks that have grown since the financial crisis; she backs tougher regulations but embraces the 2010 Dodd-Frank law that would dismantle banks posing systemic risks. He calls for $1 trillion in new spending to improve infrastructure and create jobs; she calls for $275 billion — half of what her husband’s Treasury secretary, Lawrence Summers, has advocated.