Julian Zelizer, a CNN political analyst, is a professor of history and public affairs at Princeton University and author of the forthcoming book, "Burning Down the House: Newt Gingrich, the Fall of a Speaker, and the Rise of the New Republican Party." Follow him on Twitter: @julianzelizer . The views expressed in this commentary are his own. View more opinion at CNN.

(CNN) Under normal circumstances, this would be a time of celebration for Joe Biden's campaign. With seven months left before Election day, the former vice president is now the presumptive Democratic nominee, after his last remaining opponent, Sen. Bernie Sanders, announced that he would suspend his campaign and called for his supporters to rally behind Biden.

With the party united, Biden will be able to concentrate all of his attention on the general election. He can start raising money and developing a strategy to defeat President Donald Trump in 2020.

Meanwhile, Trump continues to stumble in his efforts to govern a nation that has been locked down as a result of the Covid-19 pandemic. The economy is faltering, people are losing their lives and their jobs, and our general sense of well-being has undergone a stress test unlike any other in modern times. While we heard a great deal about malaise in the late-1970s, today the mood is one of despondency and hopelessness.

As the crisis has mounted in the past three months, the President has been repeatedly slow to respond, ignoring clear warnings and spewing disinformation, instead of confronting the problem head on. His messages often directly contradict what his own top experts have to say. And despite being someone who loves power, the President has failed to fully invoke his executive authority to ensure the production of the materials we need to fight this disease. His initial bump in the polls is now starting to slip

With an incumbent like this, there is almost no excuse for Biden to lose.

Yet Biden's obstacles to victory remain immense. Unless things miraculously return to normal in the near future, this election will be like no other in our lifetime. The coronavirus will force the Democratic Party to re-imagine what it means to run for the presidency. Without the possibility of running a ground game for at least several months, if not more, Biden and his campaign will face the real challenge of getting his message out to the public in the most surreal of times.

Biden needs to demonstrate that he can do a better job using social media to build momentum in a time when most Americans are understandably focused on the pandemic. Most Americans are barely hearing from any major Democrat these days with the exception of a handful of Democratic governors, like New York's Andrew Cuomo and California's Gavin Newsom. The news is dominated by the latest updates about the spread of the disease, as well the president's daily press briefings, which suck all the oxygen from the room.

The odds are there will be very little traditional campaigning, public appearances or televised town halls. Even the Democratic National Convention, a key event that serves to showcase the candidate, has already been postponed, with the possibility it might be held online.

The good news for Biden is that the modern media ecosystem offers many more opportunities to get out the message; ideas can be tweeted, statements can be livestreamed, and images can go viral. Indeed, President Trump has already demonstrated just how powerful these mediums can be with his prolific use of Twitter. His campaign has also shown how micro-targeted ads can be enormously effective

President Trump will certainly continue with his aggressive, below-the-belt style of politics. With the power of the executive branch behind him, Trump could conduct investigations aimed at damaging his rival and continually blast out messages aimed at destroying Biden's character. President Trump's campaign, for example, recently released an attack ad claiming Biden is soft on China, and used an image of the VP with former Washington governor Gary Locke -- an Asian American born in Seattle -- that appears to suggest he is a Chinese official.

The Biden team will also have to figure out ways to attract more interest from the television networks. Working within the limits of social distancing, Biden will also need to consider staging some events, including one in which he could name a running mate and potential cabinet appointments. He could hold regular press briefings, and make a few targeted on-site visits to factories that are shut down. This would create opportunities for Biden to explain to the public how he would build a team and do things differently than Trump.

Democrats will also have to keep pushing to ensure that there is high turnout. Given that most Republicans are resisting the call to accelerate universal mail-in voting , absentee ballots and other measures to let people vote safely, Democrats will have to take the lead at the national and state level. President Trump and Republicans realize that low turnout will benefit the GOP.

Finally, Democrats need to rethink their agenda. Biden's campaign was built around the idea that he is the anti-Trump candidate, best positioned to defeat the president -- but that may no longer be enough. The pandemic has reshaped the national agenda. The public health care system is under tremendous strain, and the economy is in tatters.

Biden needs to adjust his platform and address these problems. He needs to present a plan that will give Americans access to the health insurance they will need to cover the costs born out of this virus. And with Americans suffering through a crisis echoing the magnitude of the Great Depression, voters will need to hear how he will get this country humming again. He would also do well to promote a plan to safeguard both the health care system and the economy, should another outbreak occur.

President Trump failed to prepare for the coronavirus and waited until it was too late to respond to an epic challenge. Biden shouldn't make the same mistake when it comes to presenting his vision for a country now facing extraordinary circumstances.

The consequences of this election will be enormous. Biden has done a good job so far of beating the odds and demonstrating that he knows how to win a campaign. But he now faces not only a president who seems willing to go to any length to win reelection, but also an election that has been completely transformed in just weeks due to a global pandemic.

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What comes next will be unlike anything he has faced before. Democrats are wondering, will Biden rise to the occasion? He surprised many with his speedy victory in a crowded primary, and now many in the party are hoping that he can do this again.