Several 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).