Democratic presidential hopefuls Joe Biden and Bernie Sanders have secured crucial endorsements from prominent black supporters just days ahead of the first round of voting to pit them in a head-to-head contest.
Senator Kamala Harris, a former Democratic candidate herself, endorsed Mr Biden, while Senator Sanders won the backing of civil rights leader Jesse Jackson as the rival candidates competed for African American support - a key demographic in the fight for the party's nomination.
Voters in six states will go to the polls on Tuesday, a week after the "Super Tuesday" elections dramatically reversed the two men's fortunes, snatching the frontrunner's title from Mr Sanders and revitalising Mr Biden, who now holds a lead in delegates to the nominating convention.
Mr Biden did well on Super Tuesday in Southern states with large black populations, states similar to Mississippi, which votes Tuesday. And in Missouri, a Midwestern state also voting Tuesday, one recent poll gives him a 22-point lead.
That makes Michigan, the day's biggest prize, an almost must-win for Mr Sanders. A survey in that north-central state last week gave Joe Biden a six-point advantage.
"Joe has been there for Michigan when our back was against the wall," Governor Gretchen Whitmer said during an appearance at a majority black church in Detroit.
Michigan's critically suffering auto industry received a major boost in 2008 from a massive intervention under the administration of Barack Obama and Joe Biden.
But Ms Whitmer predicted a close race on Tuesday; Bernie Sanders has a large organisation in Michigan with considerable union support.
Also voting Tuesday are Idaho, North Dakota and Washington state.
Sanders focuses on Michigan
Bernie Sanders, desperate to kickstart his campaign after losing 10 of the 14 Super Tuesday states, has cancelled plans to speak in Mississippi, Missouri and Illinois in order to focus on Michigan.
Jesse Jackson endorsed Mr Sanders at a rally in Grand Rapids, Michigan, repaying the self-described democratic socialist for having supported his 1988 bid for the White House.
"I stand with Bernie Sanders today because he stood with me," Mr Jackson said. "I stand with him because he stands with you."
Mr Sanders touted the endorsement on today's television talk shows, calling Jackson "one of the great civil rights leaders in the modern history of this country".
"He changed American politics with the concept of the Rainbow Coalition - getting the blacks and whites and Latinos together in '84 and '88," Mr Sanders said on ABC's "This Week." "So we're proud."
Mr Sanders appeared on four Sunday talk shows; Mr Biden on none.
This morning, I announced I'm endorsing Joe Biden for president because we need someone who reflects the decency and dignity of the American people and who fights for those whose voices are too often ignored. https://t.co/H7AgCoTwd6
— Kamala Harris (@KamalaHarris) March 8, 2020
Former Vice President's Super Tuesday surge brought an influx of donations - $22 million in the past few days, his campaign said in a statement earlier.
It said $12 million would be spent on hiring new staff and launching a major media campaign in battleground states.
Ms Harris said she was backing Biden, a centrist who touts his ability to work with Republicans, because she believes he can best unify the country going into the crucial November elections against Donald Trump.
"I am with great enthusiasm going to endorse Joe Biden for president of the United States," she said in a videotaped statement posted on Twitter.
Eight other former Democratic candidates - including Pete Buttigieg, Amy Klobuchar and Beto O'Rourke - had earlier endorsed Mr Biden.
He later tweeted his thanks to Ms Harris, saying, "You've spent your whole career fighting for folks who've been written off and left behind."
The endorsement was a bit of a reversal; Ms Harris had sharply chastised Mr Biden in a televised debate last June over his warm words for past segregationist senators and his opposition in the 1970s to busing to integrate US schools.
But many African American leaders have since swung behind Mr Biden, helping to resurrect his once flagging campaign.
We look to our youth for energy, expansion and inclusion which leads to growth.
— Rev Jesse Jackson Sr (@RevJJackson) March 8, 2020
The youth that come to these rallies represent hope, healing and promise for our nation.
It's a joy to "feel the Bern" with Bernie. Keep Hope Alive! #VotingMatters @BernieSanders pic.twitter.com/FklCpzOao6
Biden favourite among black voters
Bernie Sanders, meantime, has had trouble attracting black voters – Mr Biden won more than four black votes in South Carolina for each one favouring Mr Sanders - making the endorsement from Jesse Jackson all the more significant.
In a statement posted by the Sanders campaign, Mr Jackson noted that the "black firewall" of support for Mr Biden had changed the dynamics of the race, but he questioned whether moderate policies would benefit African Americans.
"A people far behind cannot catch up choosing the most moderate path," said Mr Jackson.
"The most progressive social and economic path gives us the best chance to catch up, and Senator Bernie Sanders represents the most progressive path. That's why I choose to endorse him today."
