This weekend on The iHeartRadio Countdown with Mario Lopez we've got a brand new #1 song! Shawn Mendes has taken over the top spot with his smash hit single 'If I Can't Have You' which has been dominating the charts for a minute. His other big song right now with Camila Cabello is climbing the charts as well. So we'll countdown the rest of the top 20, play a few of Mario's favorite throwback classics and much more!
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