MICHIGAN, United States (AP) — The Democratic presidential primary is down to two major candidates, and it shows.

Former Vice President Joe Biden and Vermont Senator Bernie Sanders are spending their first weekend as their party’s last top White House contenders increasingly taking aim at one another. Each wants to show he’s the best choice before six more states — Idaho, Michigan, Mississippi, Missouri, North Dakota and Washington — vote on Tuesday.

It reflects the new contours of a race that once featured 20-plus Democrats. An increasingly bitter matchup could endure for months as Biden and Sanders compete for the right to face President Donald Trump in November.

“We have a two-person race,” Sanders said Saturday in Dearborn, a Detroit suburb with one of the nation’s largest Arab American populations. “And all over this country, people are asking themselves which candidate can best defeat Trump. I have zero doubt in my mind that, together, we are the campaign that can beat Trump.”

Sanders argues that no Democrat will win the presidency “with the same-old, same-old politics of yesteryear.” That’s ironic given that the 78-year-old Sanders is actually a year older than Biden. But the avowed democratic socialist, who has served in Congress since 1991, says he’s bucked the establishment of both parties with decades with unpopular stands that now give him the credibility to lead a political revolution “from the bottom up”.

Sanders is pledging to increase Democratic turnout by drawing younger voters, minorities and working class people to the polls even though they tend to vote in lower concentrations than many other Americans. Strong support among Hispanics lifted Sanders to victories in Nevada and California, but Biden trounced him in South Carolina and throughout much of the Deep South that voted during last week’s Super Tuesday. Biden especially ran up the score with African Americans.

Some activists are disappointed that a once diverse field of women and minorities has dwindled to two white men in their late 70s. But in Dearborn, Sanders, who is Jewish, said he was inspired by so many Arab Americans backing him. “I see people coming together from so many different backgrounds. It is beautiful,” he said.

Top advisers expect Sanders to finish strong in Washington. But he cancelled a trip to Mississippi, to focus on Michigan, Tuesday’s largest prize. He has three more Michigan events scheduled this weekend while Biden campaigns in Missouri and Mississippi.

Sanders said if he’s not the nominee, he will support Biden against Trump but “in the remaining months, I intend to make it clear what my views are and what Joe Biden’s are”.

Sanders has used many of his Michigan stops to hammer Biden’s past support for the North American Free Trade Agreement, arguing that it moved high-paying US jobs to Mexico and China while devastating manufacturing in a state dominated by the auto industry. He’s focused on Biden’s years in the Senate, when Biden backed not only trade agreements and the US-led war in Iraq, but also a ban on using federal funds to pay for abortions. Biden announced this summer that he was reversing his position on that, but Sanders said that wasn’t enough.

“I think we need a candidate that can be trusted on this issue. I am proud to tell you that I am 100 per cent pro choice,” Sanders said Friday night in Detroit.

Biden saw a surge of donor support after South Carolina and Super Tuesday, and his campaign announced that it was spending US$12 million on a six-state ad buy in places voting this Tuesday and the following week. It was his largest single advertising effort of the 2020 campaign.

He is using two television and digital ads, one promoting his relationship with President Barack Obama, the other a new effort to counter a Sanders attack on Biden’s past record on Social Security. It’s a criticism Sanders has used for months, though he hasn’t mentioned it as frequently while campaigning in Michigan.

“Biden will increase Social Security benefits and protect it for generations to come,” a narrator intones in one of the ads, before turning the matter back on Sanders. “Negative ads will only help Donald Trump. It’s time we bring our party together.”