Sanders, Biden up attacks as head-to-head race takes shape

The Democratic presidential primary is down to two major candidates, and it shows.

Former Vice President Joe Biden and Vermont Sen. Bernie Sanders are spending their first weekend as their party's last top White House contenders sharpening their attacks against one another Each is trying to demonstrate that 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 more than 20 Democrats. This state of play could endure for months as Biden and Sanders wage a protracted battle for the right to face President Donald Trump in November.

“You cannot defeat Trump with the same-old, same-old politics of yesteryear," Sanders told more than 7,000 supporters at a convention hall in downtown Detroit.

At 78, Sanders is actually a year older than Biden. But the avowed democratic socialist who has served in Congress since 1991, argues that 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 says it's part of a larger movement that can draw 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

Sanders is looking for a strong finish in Washington. But he canceled a trip to Mississippi, to focus on Michigan, the largest prize Tuesday. He was holding a rally Saturday in the heavily Arab American community of Dearborn, and had three more Michigan events scheduled this weekend. Biden was campaigning in Missouri and Mississippi.

Sanders has used his Michigan stops to hammer Biden's past support for the North American Free Trade Agreement, arguing that it moved high-paying U.S. jobs to Mexico and China while devastating manufacturing in a state dominated by the auto industry.

"Joe’s been around for a while and I’ve been around for a while. How do we differ? What’s our records? Who stood up when the going was tough?” Sanders said.

He's focused on Biden's years in the Senate, when Biden backed not only trade agreements and the U.S.-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% pro choice,” Sanders said.

Biden saw a surge of donor support after South Carolina and Super Tuesday, and his campaign announced that it was spending $12 million on a

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

“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.”