Joseph Robinette Biden Jr. has navigated a half-century in American politics by relentlessly positioning himself at the core of the Democratic Party.

Wherever that power center shifted, there Biden has been, whether as the young senator who opposed court-ordered busing in school integration cases or the soon-to-be 46th president pitching an agenda on par with Franklin D. Roosevelt’s New Deal and Lyndon B. Johnson’s Great Society.

The common thread through that evolution is Biden always pitching himself as an institutionalist — a mainstream liberal but also a pragmatist who still insists that governing well depends on compromise and consensus.

Now Biden’s central political identity faces the ultimate trial.

On Wednesday, the 78-year-old president-elect will inherit stewardship of a nation wrenched by pandemic, seismic cultural fissures and an opposition party’s base that considers him illegitimate, even to the point of President Donald Trump’s supporters violently attacking the U.S. Capitol on Jan. 6 as Congress convened to certify Biden’s victory.

Biden’s answer follows two tracks: defending the fabric of society and institutions of government that Trump’s tenure has stressed and calling for sweeping legislative action. His agenda includes an initial $1.9 trillion pandemic response, along with proposed overhauls for health care, taxation, infrastructure, education, criminal justice, the energy grid and climate policy.

“A message of unity. A message of getting things done,” Ron Klain, his incoming White House chief of staff, explained Sunday on CNN’s “State of the Union.”

The first approach, rooted in Biden’s campaign pledge to “restore the soul of the nation,” netted a record 81 million votes in the election. In his Nov. 7 victory speech, Biden called that coalition “the broadest and most diverse in history” and framed it as evidence Americans are ready to “lower the temperature” and “heal.”

Biden’s second, policy-based approach, however, still must confront a hyperpartisan age and a closely divided Congress.

The outcome will determine the reach of Biden’s presidency and further test the lifetime politician’s ability to evolve and meet events.