Bernie Sanders is attacking Joe Biden on trade policy as the two Democratic presidential hopefuls face the next round of primaries on Tuesday, with Michigan the big delegate prize of the day.

Biden led Sanders by double digits in polls of Michigan voters after the former vice president’s strong showing on Super Tuesday in states including Texas and North Carolina. Michigan offers 125 delegates, and a win there by Biden would significantly boost his fortunes in the nominating contest. Ahead of Tuesday’s voting, Biden had 664 delegates to Sanders’s 573, according to a tracker by the Wall Street Journal. It takes 1,991 to win the nomination on the first ballot at this summer’s Democratic convention.

Also see:Don’t discount the support for Bernie Sanders in Trump country.

Voters will also cast ballots Tuesday in Idaho, Mississippi, Missouri, North Dakota and Washington. Washington offers the most delegates of those five states, with 89.

“Michigan is probably the most important state on the calendar coming up [this] week,” said Brian Daingerfield of NatWest Markets, in an email to MarketWatch. “Winning in that contest will give an important message to voters about candidates viability in a state that is very likely to be among those that decide the election in November.”

Sanders told reporters he will highlight Biden’s support for trade pacts like the North American Free Trade Agreement. Biden backed that agreement in 1994.

“If we are going to defeat [President Donald] Trump in Michigan, in Pennsylvania and Wisconsin it will be very hard for a candidate who voted for these disastrous trade agreements,” Sanders said at a rally in Detroit on Friday.

The two are also sparring over Social Security, including on Twitter, where Sanders charges “one of us has a history of not only fighting cuts to Social Security but working to expand benefits.”

Biden says, “Get real, Bernie. The only person who’s going to cut Social Security if he’s elected is Donald Trump.”

Opinion:What older Americans need to know about the differences between Biden and Sanders on Social Security.

Biden and Sanders are making their fresh pushes for votes amid heightened stock-market fears over the spread of the coronavirus and an oil-price war.

Stocks DJIA, -0.46% SPX, -0.84% rallied after Biden’s Super Tuesday performance but tumbled Monday, triggering an initial circuit breaker as fears of an oil price war between OPEC and Russia sent crude futures plunging, sending shock waves through global financial markets already shaken by the spread of COVID-19.

See:Dow plunges 7.2% and S&P 500’s plunge triggers 15 minute halt at lows as oil prices deliver a punishing blow to Wall Street.

Sanders will hold a roundtable Monday with public health experts and leaders in Detroit to discuss the coronavirus, his campaign announced. Biden also has several events scheduled in Michigan on Monday.

Daingerfield of NatWest, meanwhile, said the market should coalesce around Biden as the likely nominee at this point. “Without a [Elizabeth] Warren endorsement, Sanders may struggle to recapture the early primary momentum he had, while Biden has a number of winds at his back,” said Daingerfield, citing endorsements by former primary competitors.

Also read:Elizabeth Warren ends presidential campaign, holds off on endorsement.