evidence: Freshman Rep. Alexandria Ocasio-Cortez recently captured headlines in her "60 Minutes" interview when she said the U.S. should raise taxes on a portion of the income made by America’s top earners; the idea is that once a person had made at least $10 million in a single year, every dollar coming in after that would be taxed at a rate of up to 70 percent. Many have dismissed the idea, saying it would be too radical and would damage the economy. But the Democratic representative from New York might have hit on something voters want. [...] Ocasio-Cortez has not made any official policy proposal for a higher marginal tax rate, but she is already shaping the national conversation on economic policy ahead of the 2020 elections. Former Housing and Urban Development Secretary Julian Castro, who recently announced a presidential run, has already endorsed Ocasio-Cortez’s tax hike proposal in an interview with ABC News. And while it’s still too early to know for sure, 2020 Democratic hopefuls looking to appeal to The Left may soon follow suit.