In some ways, Sen. Elizabeth Warren (D-MA) and South Bend Mayor Pete Buttigieg are an unlikely pair to be at odds: they have both used their bookish, personal approaches to politics to achieve surges of momentum in the Democratic primary. But as 2020 heads into overdrive less than 10 weeks before early voting commences, the two candidates have taken notable steps to distinguish themselves from each other over the past week. And it comes as Warren, the former Harvard Law School professor whose campaign slogan is to have a “plan” for many aspects of public governance, faces a polling challenge from Buttigieg, the multilingual Harvard alum who has taken a management consultant-style approach by pitching his policies as pragmatic.

While attempting to differentiate themselves along ideological lines (Warren has spent the majority of her candidacy promoting a broad anti-corruption platform, while Buttigieg has taken a more modest, and at times, corporate approach), the two Democrats pull from a similar supporter base of largely white, college educated voters, and have struggled to either catch on, or maintain, an economically and racially diverse coalition of supporters. And the tension between their campaigns, both vying to maintain their existing bases while each attempting to expand to new voters, has begun to bubble to the surface.

Over the past several days, the two have engaged in more direct confrontations, though still without naming the other specifically. The Daily Beast reported last month that the South Bend mayor has been subtly dinging his rivals to their annoyance, and it seems now the subtle phase is reaching an end. When a Bloomberg News reporter asked Warren about the possibility of releasing tax returns that extend to her years out of public service while she worked in the private sector, she responded by saying “my plan is to follow the same practices that were set up by Barack Obama and that is eight years of taxes.” Warren has gone a step further to release 11 years.