There has been a dramatic shift in the race for the Democratic presidential nomination over the last 48 hours, with a large number of high profile politicians throwing their support behind former vice president Joe Biden.
Most significantly, two of Biden's rivals, Pete Buttigieg and Amy Klobuchar, have dropped out of the race and publicly endorsed him.
Until this week, Buttigieg and Klobuchar were competing with Biden, but the former vice president's massive win in South Carolina led them to conclude they no longer had any realistic path to the nomination.
Their decision to drop out and endorse Biden is a sign that moderate Democrats are coalescing behind him as the only viable alternative to left-wing Senator Bernie Sanders, with just hours remaining until 14 states vote at once on Super Tuesday.
Buttigieg and Klobuchar are hardly alone.
Several other high profile Democrats have endorsed Biden since his victory in South Carolina, including former Senate leader Harry Reid, former White House national security adviser Susan Rice, former Virginia governor Terry McAuliffe and another former presidential candidate, Beto O'Rourke.
Are they all merely jumping on the bandwagon, or is something else going on?
According to NBC News, former president Barack Obama's "hidden hand" has played a subtle role in the sudden surge of support for Biden, who served him loyally as vice president for eight years.
"There appears to be a quiet hand behind the rapid movement - former president Barack Obama," NBC reports.
"People close to Obama said the former president has been keeping close tabs on the race. They said the signal has been sent in the past 36 hours that he sees Biden as the candidate to back, and they don't need Obama to say it publicly or privately."
The New York Times reports Obama spoke to Buttigieg after he dropped out yesterday, telling the former mayor of South Bend he had leverage as a former candidate and "should think about how best to use it".
Obama has repeatedly indicated he will not personally endorse anyone during the Democratic primaries, preferring to step in after the process to help unite the party for the general election against Donald Trump.
Buttigieg joined Biden in Dallas today, where he explained why he was endorsing his former competitor.
"When I ran for president, we made it clear that the whole idea was about rallying the country together to defeat Donald Trump, and to win the era for the values we share," Buttigieg said standing alongside Biden.
"That was always a goal that was much bigger than me becoming president. And it is in the name of that very same goal that I am delighted to endorse and support Joe Biden for president tonight."
Biden responded by heaping praise on the 38-year-old former mayor, saying he reminded him of his beloved son Beau, who died in 2015.
"I don't think I've ever done this before. But he reminds me of my son Beau. And I know that may not mean much to most people, but to me it's the highest compliment I could give any man or woman," said Biden.
"I look over at Pete during the debate and I think, 'You know, that's a Beau.' Because he has such enormous character, such intellectual capacity and such a commitment to other people. I can't tell you how much it means to me that he would step up and endorse me."
He urged Buttigieg to stay engaged in politics, saying there was "no limitation on what he could get done" and the only reason his presidential run had failed was his relative anonymity on the national stage.
"If Pete had been around another six years, I wouldn't be standing here. Pete would be standing, and I'd be endorsing Pete," Biden said.
And he indicated he would give Buttigieg a role in his administration, should he become president.
A couple of hours later, Klobuchar introduced Biden at a rally in Dallas.
"If you feel tired of the noise and the nonsense in our politics, and if you are tired of the extremes, you have a home with me, and I think you know you have a home with Joe Biden," she said.
"Joe Biden has dedicated his life to fighting for people. Not for the rich and the powerful, but for the mum, the farmer, the dreamer, the builder, the veteran. He can bring our country together.
"We do not, in our party, want to just eke by a victory. We want to win big, and Joe Biden can do that.
"He will not just govern with his head, but he will also govern with his heart.
"It is time for a president that will bring decency and dignity back to the White House."
Again, Biden reacted by praising his former opponent.
"Amy knows how to get things done. That's why Amy has never lost. And she's not losing now. You're going to hear a lot from Amy Klobuchar for a long, long time," he said.
The former vice president also received a surprise endorsement from O'Rourke, a popular Texas Democrat who briefly ran for president before dropping out in November.
"We need somebody who can beat Donald Trump. In Joe Biden, we have that man," O'Rourke said.
"We have someone who is the antithesis of Donald Trump. Joe Biden is decent, he's kind, he's caring, he's empathetic.
"We need somebody who can re-establish the moral authority of the United States. We need somebody who will fight for democracy here and abroad, because democracy is under attack. We need Joe Biden."
Democratic moderates are worried that Sanders, a self-described democratic socialist, will lose to Trump if he is selected to be the party's nominee.
Sanders became the undisputed frontrunner for that nomination over the last month, racking up victories in New Hampshire and Nevada as the moderate vote remained fractured between Biden, Buttigieg and Klobuchar.
Tomorrow, billionaire Michael Bloomberg will also be on the ballot for the first time, having skipped the first four states.
Today, when he was asked about the prospect of Biden consolidating moderate support, Sanders said he was not surprised or particularly concerned.
"Look, it is no secret – The Washington Post has 16 articles a day on this – that there is a massive effort, trying to stop Bernie Sanders. That's not a secret," he told reporters.
"The corporate establishment is coming together. The political establishment is coming together, and they will do everything.
"They are really getting notice that working people are standing up.
"By the way, when we talk about South Carolina, and we talk about other states, we are winning working class voters by big numbers. So they're nervous that working class people are standing up for decent wages. They're nervous that we're prepared to take on the fossil fuel industry to try to save this planet. They're nervous that more and more Americans understand that health care is a human right, not a privilege.
"So it doesn't surprise me."
Sanders' claim to have won working class voters by "big numbers" in South Carolina is dubious. Exit polling did show him winning among white voters with no college degree, but when African-Americans were added to the mix, Biden was way ahead with a margin of 50 per cent to 22 per cent.
It is true, however, that Sanders outperformed Biden significantly in the previous three states.
Buttigieg and Klobuchar's simultaneous endorsements of Biden come on the eve of Super Tuesday, which promises to be the most important day so far in the presidential race.
Iowa, New Hampshire, Nevada and South Carolina all voted one-by-one over the course of a month. Tomorrow, 14 states will vote at once. And among them are the two most populous states in the country, California and Texas.
To understand the full significance of those contests, you need a quick crash course on how the nominating process works.
Candidates are not just competing for votes; they are competing for delegates to the Democratic National Convention, which is being held in July. That is where the party's nominee will officially be chosen.
Every state in the country has a certain number of delegates to dole out. Perform well in a state, and you earn a bunch of its delegates. Do poorly, and you risk getting none.
The goal is to go the convention in July with a majority of delegates already pledged to support you. The magic number to reach a majority is 1,991.
The four states that voted before Super Tuesday awarded 155 delegates, combined. On Super Tuesday, California alone awards 415, and Texas awards 228. It marks a dramatic acceleration in the primary process.
Once the other 12 states are taken into account, an entire third of the delegates on offer throughout primaries will be won and lost in a single day.
And that is why Super Tuesday matters so much. It could be the moment when Sanders surges to an unassailable lead. Or it could leave him neck-and-neck with Biden, setting up a long, bitter fight for the nomination.
The consolidation behind Biden is particularly significant because it sets this year's Democratic primaries apart from the Republican ones four years ago.
In 2016, Trump was in a similar position to Sanders. Despite being very much an outsider, he had surged to the front of the Republican field.
The party establishment was terrified of nominating Trump, believing – wrongly, it turned out – that he would lose to Hillary Clinton.
But most of Trump's serious rivals for the nomination stubbornly refused to drop out of the race. Ted Cruz, Marco Rubio and John Kasich all stayed in for far too long, splitting the anti-Trump vote between them as he coasted to victory.
All three thought the Republican establishment should unite behind them. Instead, they ensured it never united behind anyone.
Buttigieg in particular could have decided to stay in this year's Democratic race, having won Iowa and come a strong second in New Hampshire.
But he and Klobuchar appear to have learned a crucial lesson from Republicans' failure to coalesce behind Cruz, Rubio or Kasich.
The symbolism of them appearing together to support Biden is particularly strong, as they have spent months attacking each other on the campaign trail and during debates.
Klobuchar repeatedly accused Buttigieg of being too inexperienced to run for president, having only served as the mayor of a mid-sized city.
In return, Buttigieg derided her record as a senator in Washington D.C., suggesting Americans wanted a president with a different kind of experience.
Both have now put their previous hostilities to one side in an attempt to help Biden.
With Super Tuesday looming tomorrow, we will soon learn the effect of their support.