After a strong victory in South Carolina on Saturday and the consolidation of former opponents behind his campaign, Biden performed far better than anyone expected on Super Tuesday. In states like Virginia , he generated the kind of turnout that Vermont Sen. Bernie Sanders' supporters keep promising. In Texas, he upset the pundit establishment by pulling off a dramatic victory against Sanders and Massachusetts Sen. Elizabeth Warren. As if all of that was not enough, former New York City Mayor Michael Bloomberg announced he was stopping his campaign and endorsed the former vice president. On Thursday, Warren suspended her campaign, taking away the final mainstream alternative for Democrats who don't like Sanders.

As the comedian Larry David would say on "Curb Your Enthusiasm," things are looking "pretty, pretty good" for the former vice president.

Biden's success does not dispel the concerns that have existed about his candidacy from the day he formally announced. While the desperation that Democrats feel to find a low-risk candidate who could defeat President Trump seems to have had an impact on the primaries and caucuses, the problems with Biden as a candidate remain strong. He will need to grow and nurture a robust coalition, making sure that large numbers come out to vote, despite a checkered record during his time as a public servant — on issues such as school busing, Iraq, crime and Anita Hill.

The wear and tear someone his age may feel has often been evident on the debate stage and on the campaign trail. He has always stumbled in his impromptu speeches, frequently making the kinds of gaffes that make him easy prey for opponents. And President Donald Trump will continue to try to tarnish Biden's reputation as he did with his unfounded efforts to secure a public announcement that Ukraine would investigate Biden and his son, Hunter Biden.

What can Biden do to make himself a stronger candidate as he attempts to secure the nomination?

The most important challenge is to move beyond the argument of electability.

Even though this remains the top concern of Democrats, issues do matter. We know who Joe Biden is as a person but we still need to hear more about what he will stand for as President. If Biden learns anything from his competitors' campaigns, it should be that simply promising a non-Trump presidency is not enough. Many Democrats don't think the status quo is acceptable anymore. If Biden secures the nomination, he needs to be more direct about how he envisions tackling core issues such as health care, climate change, economic insecurity, racial injustice and immigration.

As the competition within the Democratic Party fades, Biden also needs to conduct some serious outreach, just as Sanders would have to do should he pull off the nomination. On Super Tuesday, Biden, Sanders, and Warren showed that collectively they have attracted what could be an incredibly powerful coalition in November — Latinos, African Americans, younger voters, and disaffected middle-class independents. Biden can't afford to ignore those voters who didn't come into his fold. With the same fervor he has spoken about reaching out to Republicans , he needs to connect with voters who rallied and organized for his opponents and didn't think he should be the nominee.

And Biden has to stay on message. His best moments tend to come when the teleprompter is running. But there have been a number of times, including his speech after South Carolina, when he has shown that he can shine. When speaking about being a lifelong Democrat and a candidate who will always fight for the underdog, Biden can deliver a message which will resonate in many parts of the electorate. When he talks about trying to restore some stability and decency to politics, his promises might seem naïve but they are attractive in the age of President Trump. Biden will have to stay on script with the kind of discipline that he has often ignored. He has to realize that every word and every utterance, notwithstanding the fact that they come from his desire to be honest and open, will be used against him.

Finally, while continuing to promise that he will work across the aisle (a promise many observers think will never work in this age of partisanship), he must make clear he understands the new world of politics and he has to show his ability to compete on that playing field. President Trump will undoubtedly be throwing absolutely everything at Biden's campaign. People still wonder if Biden can muster the capacity to take this on and to throw it back. Now is the time to show that he can.

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At the same time, Biden has to demonstrate that he has the stamina to succeed. There have been numerous instances in the primaries, and particularly during the debates, when Biden seemed to have difficulty living up to the moment. These concerns about Biden's endurance are very real, particularly as they come on top of his own history as a flawed candidate. If Biden wants to keep building his support, he needs to prove at each high-stakes moment that he can be the candidate who shined on the national stage after South Carolina.

Based on the returns in South Carolina and Super Tuesday, it's clear that there is a coalition behind Joe Biden that might be able to recreate the magic of the 2018 midterm campaigns, this time at the presidential level. But to ensure that the support of the Democratic party is behind him, Biden must take seriously the challenges he faces as he takes on his Democratic opponents -- and then maybe Donald Trump.