Cheriss May/GettySeveral of 2020's biggest Democratic underdogs are learning a hard lesson trying to break out from the bottom: attacking Bernie Sanders as a primary campaign strategy gets you nowhere.The Vermont senator has so far retained his standing in the Democratic primary's top tier, coming in second to former Vice President Joe Biden in most polls and hauling $18 million in fundraising this quarter, the fourth highest sum. His rivals have moved in near-unison to adopt many of the policies he introduced in 2016, including a $15 minimum wage, which passed in the House this week.But with that status comes a small but vocal chorus of moderate antagonists who apparently believe hammering away at the self-avowed Democratic socialist is the best way to distinguish themselves from a crowded field. Two ex-elected officials'former Rep. John Delaney (D-MD) and former Colorado Gov. John Hickenlooper'have been leading the anti-Sanders group and by the luck of the draw, they both will be on stage during the first night of debates in Detroit later this month (though, it should be noted, Hickenlooper did not confront Sanders during last month's debate despite sharing the stage with him).But their critiques of Sanders have yet to yield any attention, in fact, both Delaney and Hickenlooper, according to recent reports, have been encouraged by their own staff to drop out of the presidential race.Delaney, who has been campaigning for the Democratic nomination since 2017, has failed to gain traction, despite spending millions of dollars to self-fund his long-shot bid. The former Maryland congressman gave up his seat in the House and started campaigning heavily in key early voting states, but polls in the low single digits.On Friday morning, Delaney's fate became even more unclear. Axios cited three sources close to Delaney who encouraged him to drop out of the race by mid-August, an account he has since called 'incorrect.''No one on my team asked me to drop out of the race and I have no plans to drop out of the race,' he said in a press release sent to reporters.Still, while he denies reporters of being asked to drop out, he also denies going hard against Sanders. 'We are not attacking Bernie, we are attacking his single payer healthcare plan, which is bad policy and bad politics,' Delaney told The Daily Beast.Over the course of his campaign, the Maryland businessman has sent several emails naming the senator directly, with a source within the campaign explicitly calling the health care strategy a 'line of attack' they are now using against Sanders.The two presidential candidates have long standing differences over the 'Medicare-for-All' debate in the Democratic Party. Sanders has made the proposal a focal point of his campaign, Delaney said the Vermont senator 'hijacked the good name of Medicare and applied it to a law that will cause upheaval in our health care system,' in an appearance with CBS' 'Face the Nation.'Still, it's those exact attacks that have left Democratic voters flat.Delaney was recently booed on stage at a progressive conference for criticizing Medicare-For-All, while several of his rivals have signed on to Sanders' original plan in the Senate. And it remains popular in polls: a recent survey by the Kaiser Family Foundation found that 73 percent of people polled support a government health plan option, while Medicare for All has polled at over 50 percent of support for roughly a year, the survey indicates.While Delaney's campaign says he primarily disagrees with Sanders over health care, Hickenlooper is expanding his criticism even further, rejecting what he describes as his 'socialist' vision for the country.'The Democratic field has not only failed to oppose Sen. Sanders' agenda, but they have actually pushed to embrace it,' Hickenlooper said recently at the National Press Club in Washington. 'Democrats must say loudly and clearly that we are not socialists. If we do not, we will end up helping to reelect the worst president in the country's history,' he said.Like Delaney, Hickenlooper has failed to gain traction in the Democratic primary, polling between zero and one percent. Unabashedly running as a moderate Democrat, the former Colorado governor has made jabbing Sanders a cornerstone of his campaign, at one point prompting Sanders to respond to criticism by posting a tweet of a speech by former President Franklin Delano Roosevelt.But there's evidence to suggest his strategy is not working. Earlier this month, Politico reported Hickenlooper's campaign was 'in shambles,' with senior aides pleading with him to drop out of the contest. Since then, multiple staffers have bolted from his campaign, including his finance director, who took a job with a rival candidate.Hickenlooper's campaign did not respond to a request for comment on his attacks on Sanders.While Delaney and Hickenlooper have unquestionably been the most vocal lower-tier critics of Sanders, others who have also criticized him as a strategy have struggled to inspire voters. Sen. Michael Bennett (D-CO) took a jab at Sanders during the first Democratic debate in Miami, but only brought in $2.8 million in fundraising this quarter, the second lowest total of any senator. Rep. Eric Swalwell (D-CA) took a shot at Biden on stage, making a generational argument that Sanders, the oldest candidate in the race, said called 'ageism.' Swalwell dropped out of the race shortly after his performance.Sanders is scheduled to debate on Tuesday, July 30 in Michigan, a state he won in an upset victory over Hillary Clinton in 2016. In addition to Delaney and Hickenlooper, he's slated to share a stage with lower-tier contenders who are decidedly more moderate, including Sen. Amy Klobuchar (D-MN), Montana Gov. Steve Bullock, and Rep. Tim Ryan (D-OH), who will have ample opportunity to test-run attacks against one of the leading progressives on stage.Read more at The Daily Beast.Get our top stories in your inbox every day. 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