<a href="http://www.cnn.com/specials/politics/joe-biden-news" target="_blank">President Joe Biden</a> embraced a familiar role on his trip to Houston Friday, offering both comfort and federal support after a severe winter storm-battered Texas and <a href="http://www.cnn.com/2021/02/17/us/texas-winter-storm-how-to-help-iyw-trnd/index.html" target="_blank">left millions without power, heat or water</a>.

It’s a role past presidents have stepped into amid disasters and tragedies