WASHINGTON (AP) — Elizabeth Warren and Pete Buttigieg have intensified their spat that puts a new focus on tensions between the party’s progressives and moderates in the Democratic presidential nomination.

She scolded Mayor Buttigieg of South Bend over attending closed-door fundraisers, and his camp quickly fired back.

The debate exposes tensions about Warren’s strongly progressive platform, featuring a stiff wealth tax, universal health care and “structural changes” that would reshape the political system, and whether it may be too ambitious to survive a general election battle with President Donald Trump.