The Green New Deal has emerged as a key litmus test for prospective 2020 presidential candidates, with high-profile candidates jumping on board to back the progressive environmental pitch. On Sunday, Sen. Amy Klobuchar (D-Minn.) entered the 2020 race after supporting the proposal. Four other senators who have declared presidential bids have co-sponsored the resolution, and Sen. Bernie Sanders (I-Vt.), who is mulling a 2020 campaign and has previously supported the concept, will back the plan. Their support highlights one of the progressive ideas at the center of the Democratic race, while the Republican National Committee dismissed the proposal as a...