Tonight on the Last Word: AG William Barr defends helping convicted Trump aide Roger Stone while criticizing Trump’s tweets. Also, Sen. Elizabeth Warren responds to Mike Bloomberg’s past comments on redlining and the 2008 housing market collapse. Plus, Democrats look ahead to the Nevada caucuses. And a former Ohio State wrestler claims Rep. Jim Jordan asked him to deny allegations of sexual abuse by an OSU doctor. Dahlia Lithwick, Joyce Vance, Matt Miller, Maria Teresa Kumar and John Heilemann also join Lawrence O’Donnell.