Two experienced female Senators walk into a presidential debate. Both are trailing in the polls behind an inexperienced male mayor with some glaring political weaknesses. Both know that this debate is a make-or-break moment, one that could decide whether they advance to the next phase of the campaign.

And yet, the two moments that Sen. Kamala Harris and Sen. Amy Klobuchar sparred with Mayor Pete Buttigieg amount to a case study for how gender works in the 2020 campaign. Men are rubber, women are glue: if you’re a female candidate, you know that your attacks on your male rivals may bounce off him and stick to you.

Every time Harris and Klobuchar were poised to whack Buttigieg, they pulled their punches. They faltered. They softened the blow. Those moments were instructive. They were not evidence that Harris and Klobuchar can’t fight; both are former prosecutors who know how to go for the jugular (and have demonstrated that ferocity on the public stage). And they were not evidence of Buttigieg’s comparative strength on either substance or political viability; Harris rose through the ranks of California politics to be the first black woman elected state attorney general, and Klobuchar is one of the most productive and bipartisan members of the Senate, having passed more than 100 bills, many with Republicans. (Buttigieg’s major accomplishments as mayor in South Bend include expanding the roads and revamping the downtown.)