WASHINGTON - U.S. Democrats are ready Tuesday to officially proclaim former U.S. Secretary of State Hillary Clinton as their 2016 presidential nominee, making her the first U.S. woman ever to become a major party standard bearer in the race for the White House.

In the time-honored tradition of U.S. presidential nominating conventions, state delegations, one after another at the party's quadrennial gathering in Philadelphia, Pennsylvania, will cast a majority of votes for Clinton, a fixture on the American political scene for a generation.

Her challenger through months of campaigning, Vermont Senator Bernie Sanders, is calling for his supporters to vote for him, but acknowledges he won't overtake her.

He gave a rousing convention speech Monday night endorsing Clinton and could nominate her to show some semblance of party unity in the campaign against Republican contender Donald Trump, the real estate tycoon who claimed his party's nomination last week.

Former Democratic Presidential candidate Sen. Bern
Former Democratic Presidential candidate Sen. Bernie Sanders takes the stage during the first day of the Democratic National Convention in Philadelphia, July 25, 2016.

Main Speakers Tuesday at DNC

Bill Clinton's role

With her nomination secure, Clinton's husband, former President Bill Clinton, the U.S. leader through much of the 1990s, takes center stage Tuesday to make the case why Americans should vote for her in the November national election to become the country's 45th president when President Barack Obama leaves office in January.

His support for his wife is complicated, however, by the fact that the progressive wing of the U.S. Democratic Party that supported Sanders has turned against some of the 42nd president's accomplishments, including support for free trade and tough criminal justice reforms that sent many people, especially racial minorities, to prison for lengthy terms.

Hillary Clinton is locked in a tight race with Trump. Several polls show Trump edging ahead of her at the moment, buoyed by new support after Republicans attacked Clinton's credibility for four nights at their convention.

It is the Democrats' turn this week and convention speakers wasted no time Monday in denouncing Trump, painting him as an insensitive, me-first businessman unqualified to become the American leader.

FILE - First lady Michelle Obama speaks at the Dem
First Lady Michelle Obama spoke of the importance of those in the White House serving as role models to the nation's children at the Democratic National Convention in Philadelphia July 25, 2016 (A. Shaker/VOA)

First lady's endorsement

First lady Michelle Obama led the attack on Trump, saying, “I am here tonight because in this election there is only one person who I trust with that responsibility, only one person who I believe is truly qualified to be president of the United States, and that is our friend Hillary Clinton.”

Without naming him, the first lady scoffed at Trump's campaign slogan "Make America Great Again."

"Don't let anyone ever tell you that this country isn't great, that somehow we need to make it great again, because this right now is the greatest country on earth," she said.

Sanders, in his speech, said, "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.”

Trump criticized Sanders on Twitter, saying he "totally sold out" to Clinton and that his campaign was a "waste of time."

But many of Sanders' supporters have remained adamant in their opposition to Clinton's nomination, believing she is too closely linked to Wall Street financial chiefs and still favors overseas trade deals to the detriment of U.S. workers, even as she has disavowed her original support for a 12-nation Pacific Rim deal that President Obama has championed.

Email hack

Sanders supporters are particularly incensed at some of the content in nearly 20,000 emails sent by Democratic leaders that were disclosed over the weekend by WikiLeaks. The emails showed party officials disparaged the Sanders campaign during the long party contest for the presidential nomination and favored Clinton.

Demonstrators make their way around downtown, July
Demonstrators make their way around downtown, July 25, 2016, in Philadelphia, during the first day of the Democratic National Convention.

Party officials have blamed the leak of the emails on "Russian state actors," hacking of party headquarters computers that U.S. security experts say was a possibility, but a contention that Trump has mocked. The U.S. Federal Bureau of Investigation says it is investigating the breach at the Democratic National Committee.

On Tuesday, Russian Foreign Minister Sergei Lavrov rejected any allegation that Moscow was responsible for the computer attack.   
Other convention speakers Tuesday include House Minority Leader Nancy Pelosi, interim party chair Donna Brazile and a group of mothers whose children have died from gun violence or in clashes with police.