While Super Tuesday ballots were still being counted Wednesday, Sen. Bernie Sanders launched the next phase of his Democratic presidential campaign with a trio of television advertisements in mid-March primary states directly and indirectly challenging his top competitor, former Vice President Joe Biden.After Sanders on Tuesday won at least four states—including the biggest, California—and Biden performed better than expected nationwide in the single-largest day of primary voting, political commentators began framing the contest as \u0022a two-person race for the future of the Democratic Party and the country.\u0022The new TV ads, produced by Sanders\u0026#039; in-house team, are airing in states scheduled to vote on March 10 (Idaho, Michigan, Mississippi, Missouri, and Washington) and March 17 (Arizona, Florida, Illinois, and Ohio). It is unclear if the ads will also target North Dakota, which is set to hold caucuses on March 10.A Sanders advertisement titled \u0022Protect Social Security\u0022 swipes at Biden for his record on not only that social safety net program, but also Medicare and Medicaid. The ad features audio of the former vice president recalling his argument for a federal spending freeze, followed by Sanders saying: \u0022Well, we\u0026#039;ve got some bad news for them. We are not gonna cut Social Security. We are gonna expand benefits.\u0022Sanders senior adviser Warren Gunnels shared the ad on Twitter Wednesday and wrote: \u0022Joe Biden has a 40-year history of working with Republicans to cut Social Security. Bernie Sanders has a 30-year record fighting to expand Social Security and prevent cuts.\u0022Another Sanders ad employs a tactic already used by his fellow competitors: footage of former President Barack Obama praising the candidate. \u0022Bernie is somebody who has the virtue of saying exactly what he believes. Great authenticity, great passion, and is fearless,\u0022 the last Democratic president says in the ad.Despite reporting in recent days that Obama has privately spoken with some candidates, he has declined to publicly endorse anyone—including Biden, his vice president for both terms—so far.While some reporters noted that the Obama ad \u0022leaves out context\u0022 and wrote that the move raises eyebrows, given that Sanders has \u0022stood out among elected officials [as] one of the 44th president\u0026#039;s fiercest left-leaning critics,\u0022 other commentators and Sanders supporters commended the campaign for being politically \u0022savvy.\u0022Holy shit this new ad is exactly what Sanders should be doing btwn now \u0026amp; next Tuesday. It is insane how nimble \u0026amp; savvy his campaign is. Hats the fuck off. pic.twitter.com/D3sZLqF1pv— rob delaney (@robdelaney) March 4, 2020This Bernie ad ft Obama is airing right now in Florida. This is the sneakiest thing I’ve seen the Sanders campaign do so far. And it’s long overdue and right on point. If the DNC thinks Sanders is backing down easily again like in 2016, they’re more out of touch than i thought. pic.twitter.com/xx5Zf4aPfk— Armani (@historyofarmani) March 4, 2020In a comment to NBC News national political reporter Sahil Kapur, Biden campaign spokesperson Andrew Bates hit back by touting the former vice president\u0026#039;s service in Obama\u0026#039;s administration:Biden campaign spokesman @AndrewBatesNC responds to the new Sanders ad featuring Obama\u0026#039;s words of praise for Bernie. pic.twitter.com/5qVvpzLzV6— Sahil Kapur (@sahilkapur) March 4, 2020The final ad features union autoworker Sean Crawford explaining that he supports Sanders\u0026#039; second presidential bid because he is the only candidate who \u0022has consistently opposed every disastrous trade deal\u0022 that has \u0022decimated\u0022 Crawford\u0026#039;s community.\u0022The banksters that have been robbing us blind and stealing our pensions and destroying our communities, they have something to worry about,\u0022 Crawford says. \u0022This is a man of conviction, a man of integrity, a man that is going to stand up for you no matter what.\u0022Although the ad is about Sanders\u0026#039; support for working people and makes no mention of Biden, the former vice president has fought for endorsements from labor unions across the country and has famously called himself \u0022middle-class Joe.\u0022The ads followed a memo for Sanders staff and surrogates, authored by campaign manager Faiz Shakir and senior adviser Jeff Weaver, that was first published by the Washington Post before polls closed Tuesday. The memo declared that \u0022we are now entering the phase of the primary in which the differences between Bernie and Biden will take center stage.\u0022As Common Dreams reported Tuesday, the memo also highlighted Biden\u0026#039;s record on Social Security cuts as well as some of his key votes when he represented Delaware in the U.S. Senate; Biden backed the 1994 North American Free Trade Agreement (NAFTA), the 2003 invasion of Iraq, and the 2005 bankruptcy bill.Only Sanders, Biden, Rep. Tulsi Gabbard (D-Hawaii), and Sen. Elizabeth Warren (D-Mass.) remained in the race as of press time. However, Gabbard and Warren\u0026#039;s respective poor performances in the Super Tuesday primaries fueled speculation over how much longer they will continue their campaigns.