President Biden’s task Thursday night was daunting as he marked the first anniversary of the week when the coronavirus forced America to shut down. He needed to acknowledge the loss of more than 529,000 lives to the coronavirus pandemic and the accompanying economic suffering, while offering a sense of optimism that the future can and will be brighter.

The first 50 days of Biden’s presidency have offered examples of his leadership style — and how it differs so dramatically from that of former president Donald Trump. Thursday’s speech from the White House provided another revealing glimpse. Instead of a president saying, “I alone can fix it,” Biden said he can only succeed with the help of others.

Leaning against the lectern and looking directly into the camera, he said, “I will not relent until we beat this virus. But I need you, the American people. I need you. I need every American to do their part.” That contrast in leadership styles underscored what the transition from the 45th president to the 46th has meant.

Midway through his first 100 days in office, Biden might have been tempted to use his first nationally televised speech merely to take a modest victory lap over the passage of the nearly $2 trillion coronavirus relief package that he signed into law earlier on Thursday. That will come soon enough. Instead, mixing empathy with hard realities, he provided a blueprint for returning the country to some sense of normalcy by summer, while appealing to all Americans to help him make it happen.

Biden made many promises during his campaign for the White House, but none more important than to lead a national effort to defeat the scourge of the coronavirus pandemic, and that has been almost a singular focus. In the months ahead, he will face difficult battles to fulfill pledges on climate change, immigration, infrastructure, racial justice and voting rights. Even now, he is struggling with a growing crisis of unaccompanied minors on the southern border that threatens to get worse.

But the success of his presidency will rest in large part on winning this first big battle against the virus. The reality he outlined underscored that America is still far from victory. The country remains in a race, pitting the goal of vaccinating most adults as quickly as possible against the threat of virus variants that are spreading rapidly and that potentially require a new round of shutdowns and economic dislocations.

That may be why the president emphasized what remains to be done as much as what already has been done. To a nation exhausted from a year in shutdown, Biden offered hope. He set a goal of having families and friends able to gather together to celebrate the Fourth of July, and he ordered states to make all adults eligible for the vaccine by May 1, earlier than previously expected.

But with hope came words of caution. He warned against backsliding in behaviors that could allow new variants of the virus to spread and set back the timetable for a return to normal. That means continuing to wear masks and practice social distancing, and getting vaccinated as soon as possible once eligible.

Things today are better than when Biden took office, but he and his team have not done this alone. Development of the vaccines began during Trump’s administration, and the rollout, halting as it was, started before Biden was sworn in. Still, in the first months of the new administration, two things have happened.

First, availability of vaccine supply has increased, and so too has the pace of shots administered, dramatically so. Second, Biden won a major victory with the passage of the American Rescue Plan over united Republican opposition. He signed it into law hours before his speech, and he and Vice President Harris will mark that win on Friday with a ceremony at the White House before traveling around the country to sell the plan.

Faced with a choice of trying to win even minimal support from Republican lawmakers or plowing forward as quickly as possible without them, Biden never hesitated to push ahead. He was criticized for seeming to abandon his calls for unity on Inauguration Day, but lessons learned from his days as vice president shaped the thinking of his team: Go as big as possible as quickly as possible with legislation, and don’t hold out hope for long for getting help from Republicans.

Amid outside predictions that the size of the final package would have to shrink by as much as a few hundred billion dollars, Biden held firm, agreeing to just enough tweaks to win the support of Sen. Joe Manchin III (D-W.Va.). That and a ruling from the Senate parliamentarian that stripped out the proposal that would have gradually raised the federal minimum wage to $15 an hour provided the formula to assure passage.

Now, administration officials say, they are applying another lesson from the Obama years, which is not to take for granted that they will receive the political credit they believe they deserve for the benefits in the new legislation. In selling the plan over the coming weeks, in trying to alert Americans to the benefits that are included in the pathbreaking package, Biden and Harris will try to blunt Republican criticism and hold public opinion on their side.

On this task, Biden starts in a good place. The measure enjoys popular support in the polls, including among a significant percentage of Republicans. A Pew Research Center study released this week found that 70 percent of Americans say they favor the legislation, including 41 percent of Republicans. A majority say the Biden administration made a good-faith effort to seek bipartisan compromise, while a majority say Republicans did not.

Those are helpful numbers as Biden starts the next phase in the fight against the virus. But there is no guarantee that they will hold. Having succeeded in getting his legislation approved, Biden must do what he can to get buy-in from Americans to heed the advice of the Centers for Disease Control and Prevention and infectious-disease expert Anthony S. Fauci. Already, some states are moving far faster than those guidelines would suggest in opening their economies and, in some cases, eliminating mask mandates.

The 100-day mark of any presidency is an artificial milestone, as the work of an administration cannot truly be measured in such a short period. Half that number of days is even more artificial. But few presidents have confronted the severity of the problems that greeted Biden when he took the oath of office, which is why there is as much focus on the progress or lack thereof of this president.

He has brought a new tone to the White House but knows that tone by itself is not how he will be judged. In another 50 days, or perhaps another 50 after that, Americans will know whether he, with their help, has begun to meet the biggest test of his young presidency.