The Democratic nomination Tuesday night became Hillary Clinton's to lose – and her commanding wins in Maryland, Pennsylvania and Delaware mean there is almost no way she can fail in her second, grueling quest to be the first female major party presidential nominee.
Speaking in Philadelphia, the city where Clinton would be officially crowned the nominee, the former secretary of state talked like a general election candidate, slamming the GOP for what she called divisive and negative rhetoric.
"We will unify our party to win this election and build an America where we all rise together, an America where we lift each other up instead of tearing each other down," a beaming Clinton told cheering supporters.
She made merely a passing criticism of her opponent, Sen. Bernie Sanders of Vermont, whom she has characterized as long on pie-in-the-sky rhetoric and short on plans. "We have to be both dreamers and doers," Clinton said.
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Warren Buffett, chairman and chief executive officer of Berkshire Hathaway Inc., smiles during an event with Hillary Clinton, former Secretary of State and 2016 Democratic presidential candidate, in Omaha, Nebraska, U.S., on Wednesday, Dec. 16, 2015. Buffet said at the rally that he was supporting Clinton's bid for president because they share a commitment to help the less affluent. (Photographer: Daniel Acker/Bloomberg via Getty Images)
Governor Jerry Brown, seen here with then-candidate Bill Clinton in 1992, notoriously did not like the Clintons for years, but announced a week before the California primary that he would back Hillary Clinton. (Photo by Cynthia Johnson/Getty)
Actor Leonardo DiCaprio, seen here at the 2016 Vanity Fair Oscar Party, hasn't formally endorsed Hillary Clinton but he has donated $2700 to her campaign and backed her in 2008. (Photo by Axelle/Bauer-Griffin/FilmMagic)
Walter Mondale was the first former Democratic vice president to endorse Clinton (REUTERS/Craig Lassig)
Rep. John Lewis, D-Ga., has been an early Clinton backer, seen here at a 'Super Tuesday' watch party her campaign in Atlanta, Ga., March 1, 2016. He is famous for his work fighting for civil rights alongside Dr. Martin Luther King Jr. (Photo By Tom Williams/CQ Roll Call)
LEBANON, NH - JANUARY 09: Former U.S. Women's National Soccer Team captain Abby Wambach smiles while she is introduced to a crowd at a Hillary Clinton campaign office on January 9, 2016 in Lebanon, New Hampshire. Wambach highlighted Democratic presidential candidate Hillary Clinton's commitment to standing up for women and girls. (Photo by Scott Eisen/Getty Images)
Singer Demi Lovato, seen here onstage at WE Day California 2016, is a Clinton supporter. (Photo by Mike Windle/Getty Images for WE Day )
Actress and screenwriter Lena Dunham campaigns for U.S. Democratic presidential candidate Hillary Clinton at Eight Seven Central screen printers in Des Moines, Iowa, January 9, 2016. REUTERS/Brian C. Frank
Singer Katy Perry, center, holds a sign in support of Hillary Clinton, former U.S. secretary of state and 2016 Democratic presidential candidate, as Clinton speaks at the Jefferson-Jackson Dinner in Des Moines, Iowa, U.S., on Saturday, Oct. 24, 2015. With Vice President Joe Biden officially out of the presidential race, the nation's first nominating contest between front-runner Clinton and Senator Bernie Sanders is gaining steam, according to a new Bloomberg Politics/Des Moines Register Iowa Poll. Photographer: Daniel Acker/Bloomberg via Getty Images
Senate Minority Leader Harry Reid, seen here working with Clinton when they were Senate colleagues, was an early supporter of the former secretary of state. (REUTERS/William Philpott WP/SV)
Actress Kerry Washington, seen here at a 30th anniversary presentation at the 2015 Film Independent Spirit Awards, is a Clinton supporter. (Adrees Latif / Reuters)
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Sanders won the nation's smallest state, Rhode Island, in a victory that served as a metaphor for a candidate who has done far better than expected but still always lagged behind the front-runner.
Clinton's win makes it all but mathematically impossible for Sanders to catch up, especially with Clinton's dominance among the "superdelegates," elected officials and party bigwigs who get a say in selecting the nominee at the convention. But Sanders has shown no indication he will drop out of the race, a move that would allow Clinton to focus on the general election but take the once-relatively unknown Vermont lawmaker out of the national spotlight.
Sanders' campaign has made noises about convincing superdelegates to switch sides once the nomination comes to a vote in Philadelphia in July. But that possibility seems even more dim with Clinton's performance Tuesday night. Aside from winning lopsided victories in three states, Clinton dominated among women and African-Americans, both critical Democratic constituencies.
But the enthusiasm for Sanders has turned out to be no match for the strategic work of an experienced Clinton campaign, which started early in wooing superdelegates and local political and civic leaders. Clinton eschewed the huge rallies and instead has done smaller events aimed at targeted audiences.
That plan was rewarded with a 16-point victory for Clinton in New York, a primary Nelson sees as the turning point for the Sanders campaign. While Sanders was rallying a crowd of 28,000 in Brooklyn, Clinton was addressing a small crowd on mostly-Republican Staten Island, listing her accomplishments as senator from New York. She ended up taking Staten Island – along with Sanders' home borough of Brooklyn.
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PHOENIX, AZ - MARCH 15: Democratic presidential candidate Sen. Bernie Sanders (D-VT) speaks to a crowd gathered at the Phoenix Convention Center during a campaign rally on March 15, 2016 in Phoenix, Arizona. Hillary Clinton won the Democratic primary elections in Florida, North Carolina and Ohio, while Missouri and Illinois remain tight races. (Photo by Ralph Freso/Getty Images)
DES MOINES, IA - JANUARY 26: Democratic presidential candidate Sen. Bernie Sanders (I-VT) speaks to the media after holding a campaign event with United Steelworkers Local 310L, on January 26, 2016 in Des Moines, Iowa. Sanders continues his quest to become the Democratic presidential nominee.. (Photo by Joe Raedle/Getty Images)
TOPSHOT - US Senator and Democratic Presidential Candidate Bernie Sanders speaks during a campaign event at the University of Northern Iowa in Cedar Falls, Iowa, January 24, 2016, ahead of the Iowa Caucus. / AFP / JIM WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)
Senator Bernie Sanders, an independent from Vermont and 2016 Democratic presidential candidate, participates in the Democratic presidential candidate debate in Charleston, South Carolina, U.S., on Sunday, Jan. 17, 2016. Hours before Sunday's Democratic debate, the two top Democratic contenders held a warm-up bout of sorts in multiple separate appearances on political talk shows, at a time when the polling gap between the pair has narrowed in early-voting states. Photographer: Patrick T. Fallon/Bloomberg via Getty Images
NEW YORK, NY - JANUARY 05: Democratic presidential candidate Sen. Bernie Sanders (I-VT) shakes hands with supporters after outlining his plan to reform the U.S. financial sector on January 5, 2016 in New York City. Sanders is demanding greater financial oversight and greater government action for banks and individuals that break financial laws. (Photo by Andrew Burton/Getty Images)
LEBANON, NH - NOVEMBER 11: Presidential candidate Bernie Sanders (I-VT) marches in the Veterans Day Parade November 11, 2015 in Lebanon, New Hampshire. Sanders goes into the Democrats second debate this weekend still running strong in the polls.(Photo by Darren McCollester/Getty Images)
Senator Bernie Sanders, an independent from Vermont and 2016 Democratic presidential candidate, speaks at the Congressional Hispanic Caucus Institute conference in Washington, D.C., U.S., on Wednesday, Oct. 7, 2015. While next Tuesday's first Democratic presidential debate will probably lack the name-calling and sharp jabs of the Republican face-offs, there's still potential for strong disagreements between the party's leading contenders. Photographer: Andrew Harrer/Bloomberg via Getty Images
Democratic Presidential candidate Senator Bernie Sanders speaks about the Workplace Democracy Act on Capitol Hill in Washington, DC on October 6, 2015. AFP PHOTO/JIM WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)
US Senator from Vermont and Democratic presidential candidate Bernie Sanders addresses striking low-wage contract workers from the US Capitol and religious leaders at the Lutheran Church of the Reformation in Washington, DC, on September 22, 2015 for an interfaith service ahead of the arrival of Pope Francis for a six-day visit to the US. AFP PHOTO/NICHOLAS KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)
MANCHESTER, NH - SEPTEMBER 19: Democratic Presidential candidate Senator Bernie Sanders (I-VT) talks on stage during the New Hampshire Democratic Party State Convention on September 19, 2015 in Manchester, New Hampshire. Five Democratic presidential candidates are all expected to address the crowd inside the Verizon Wireless Arena. (Photo by Scott Eisen/Getty Images)
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The Vermont lawmaker was also damaged, Nelson notes, by an interview he gave to the New York Daily News editorial board in which Sanders appeared to have an unformed foreign policy and no specific plan to break up the big banks, as he repeatedly has pledged to do.
Pennsylvania and Maryland were challenging for Sanders from the start, as both have traditional Democratic constituencies, such as African-Americans in both states and an older electorate in the Keystone State, that have favored Clinton in primaries so far.
The question Democrats have is: What does Sanders want? And how will he conduct himself for the remainder of the campaign?
Sanders has said he wants to shape the party's message and platform, meaning in practical terms that he would be given a speaking role at the convention. That might be hard for Democrats to swallow if Sanders continues to criticize Clinton aggressively. Her camp is particularly irritated with Sanders' charges that Clinton is getting around campaign finance rules, since it feeds Republican Donald Trump's "Crooked Hillary" line of attack.
Clinton would need Sanders supporters to embrace her – or at least vote for her – in November, and that would require Sanders to endorse Clinton formally. Since Sanders was not even a Democrat until he sought the party's nomination for president, he has no established ties or loyalty to the party, notes Nelson, who adds that Sanders ran against Democrats on 10 occasions in his career.
But if he refuses to endorse Clinton – who not only endorsed President Barack Obama but urged delegates to nominate Obama by acclamation despite having endured a bitter 2008 primary campaign against him – he will likely be denied a formal role in Philadelphia, Nelson predicts. California Gov. Jerry Brown, who ran for president in 1992, was refused a convention speaking role in New York City that year because he declined to endorse Bill Clinton.
"You can be damn sure the Clintons will impose the same on Bernie if he chooses not to endorse her," Nelson says.