Sanders struggles to repeat 2016 win in Michigan

"This primary on Tuesday is going to be the watershed moment in this race," said Michigan state Senator Jeff Irwin, who has endorsed Sanders.

"We must bring more people into this movement," said Rep. Alexandria Ocasio-Cortez (D-NY), joining in the recent acknowledgment from Sanders that his 2020 bid has not energized young voters and increased turnout in the Democratic primaries.

Sanders used two rallies on Sunday to celebrate his biggest endorsement since Super Tuesday, as civil rights leader Jesse Jackson appeared at a Sunday rally with Sanders in Grand Rapids.

"If there was no Jesse Jackson - in my view - there would not have been a President Barack Obama," Sanders said.

But if Sanders was hoping to use his Jackson endorsement to spur greater support in the black community, there were very few black voters at his Ann Arbor rally on Sunday.

Sanders has thrown everything he has into Michigan in the past few days, tacitly admitting that he must win this state, or his bid for the White House could well be on the rocks in 2020.

The schedule was in flux for Sanders in recent days, as his campaign scheduled - and then canceled - campaign stops in Mississippi, Missouri, and Illinois.

At the same time, Sanders added a series of events all around Michigan, trying to recapture the spirit of 2016, when he defeated Hillary Clinton in the Wolverine State.

"I didn't know there were this many people in Grand Rapids," Sanders told a big outdoor crowd gathered on Sunday, as his anthem, "Power to the People" played on the loudspeakers.

Sanders even added a Monday afternoon event on the Coronavirus to try to attract a little more attention before Tuesday's vote, where Michigan is the top delegate prize.

Meanwhile, Joe Biden was moving methodically through Mississippi and Missouri this weekend - arriving on Monday for a series of events in Michigan.

"Thanks for having my back, I'll have yours," Biden said to cheers at a stop in Jackson, Mississippi.

In his place in Michigan were Democratic lawmakers in Congress, urging on volunteers to get out the vote on Tuesday.

"Joe had a big week, starting in South Carolina, and that momentum, yes indeed," as Rep. Anthony Brown (D-MD) was drowned out by cheers inside a union hall in Detroit.

"We need somebody who can help restore our standing in the world," said Sen. Tom Carper from Biden's home state of Delaware.

"And I know of no one better to do that than Joe Biden," Carper added.