At 11:11 p.m. Monday, as high rainy winds flailed Philadelphia, the Democratic Party exhaled.

The white-haired man with the thick Brooklyn accent said the words that needed to be spoken if there was to be any hope for party unity.

"Any objective observer will conclude that based on her ideas and her leadership, Hillary Clinton must become the next president of the United States; the choice is not even close."

Clinton understands importance of diversity1:31

The Wells Fargo Arena erupted in cheers, perhaps of relief more than anything else.

But off to the side, to the left of the white-haired man at the podium, hundreds of Bernie Sanders delegates booed. Many cried. Some sat in their seats dazed. And angry. Some had their mouths taped shut with the words: "Silenced by DNC."

Some had been with him in soul and spirit for more than a year, since the senator from Vermont began his crusade that became a movement.

Month after month, he hammered away at Hillary Clinton, mocking her as, at best, a status quo establishment hack, and at worst, a tribune of Wall Street.

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Senator Bernie Sanders has encouraged his supporters to get behind Democratic presidential nominee Hillary Clinton, but it's going to be up to Clinton to win many of them over with her convention speech Thursday night. (Brian Snyder/Reuters)

In primaries and caucuses he won here and lost there, he pounded out the same arguments of progressivism — high taxes on wealth, free college education, higher minimum wage and tougher banking regulations.

Like the great Democratic populist of the past, William Jennings Bryan, he thundered against privilege and power and in the doing, forced Hillary Clinton and the party hierarchs to move cautiously to the left.

Bad start

The historic week didn't start well for the Democrats. Leaked emails from the Democratic National Committee proved what Senator Sanders had been saying all along: the DNC had regularly thumbed the scale in favour of Clinton.

But unlike the Republicans, who had a Day 1 fiasco with the plagiarism scandal, the Democrats did something about it.

DNC chairwoman Debbie Wasserman Schultz bowed to the not-so subtle pressure from her party and announced Sunday she'll step down following the convention. The next day, interim chairwoman Donna Brazile issued a strong apology to Sanders on behalf of the entire national committee.

There are other differences with last week's GOP convention in Cleveland.

For one thing, there are more people in the arena.

For another, the delegates and alternates here in Philadelphia are younger and more diverse than the Republicans who gathered in Cleveland.

Most Trump supporters seemed to be middle- to late-middle-aged white males.

And while Republicans were pleased to nominate the unlikeliest candidate in the history of their party, most Democrats were ecstatic Tuesday when they nominated the first woman with a very good chance of becoming president.

'Cold,' 'Brilliant'

Which brings it all down to Hillary Rodham Clinton, who's described herself as "a very well-known unknown person."

When asked about Clinton in the arena Monday night, the answers from delegates were as varied as they were entrenched.

She is cold, she is brilliant, not a person you can warm to, a fighter for women's rights her entire life, the best-equipped person to run the country.

When you talk to the Bernie or Bust acolytes, you come away with the impression they would rather anybody but Hillary Clinton.

Even though Sanders told supporters Monday, "I am proud to stand with her."

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Two Sanders supporters hug at the end of his speech during the first session at the Democratic National Convention in Philadelphia. (Reuters)

It does seem Clinton might be right when she said: "Everybody else has a margin for error. I don't."

It will be up to her to restore and nurture party unity.

Chance to make more history

Democrats have been divided at convention time before. It's nothing new.

In 1968, after the Battle of Chicago, disaffected Democrats finally came together to work for their candidate Hubert Humphrey and give Richard Nixon a run for his money.

In 1948, the last time the Democrats held their convention in Philadelphia, the party was split wide open over the debate between state rights and human rights.

Dozens of delegates from the states of the Old Confederacy walked out.

Democrat Harry Truman went on to win re-election by promising that his party would continue to be "the haven of ordinary people of this land and not of the favoured classes or the powerful few."

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Delegates celebrate after U.S. presidential candidate Hillary Clinton won the Democratic presidential nomination at the convention. (Reuters)

Much, if not most, of the drive to unity will depend on what Clinton says Thursday night.

She has to reach out to the diehard Sanders supporters, the young, the progressives, and persuade the viewing audience that her extraordinary resume is an asset, not a hindrance.

She made history this week. If she can bring the party together, she will make history again come November.