North American Politics Headlines at 4:25 p.m. EDT

The Latest: Sanders cancels Cleveland rally over virus fears

At White House, insurers again pledge no-cost virus tests

Moderate Democrats see edge in challenges from progressives

Stakes rise for Sanders heading into Michigan primary

6 questions heading into next set of Democratic primaries

Edited Biden video portends social media challenges in 2020

Melania Trump cancels fundraiser, cites scheduling conflict

First lady urges PTA to teach positive behavior to children

Trump says sexism not to blame for end of Warren's campaign

One more victory: Biden wins most Super Tuesday delegates