text:  That's NPR's Liz Baker reporting. Trump is expected to deliver a message of unity at the convention taking place two days after he was injured in an attempted assassination during a rally in Pennsylvania. President Biden has spoken out against political violence as his reelection campaign continues to be tested over concerns from within his own party about his mental acuity and ability to defeat Trump in November. Biden is participating in an interview with NBC's Lester Holt, which airs tonight.