CNN chief data analyst Harry Enten said Democrats have a “big siren warning sign" ahead of Election Day and it is close polling margins in key Senate toss-up races. Enten said the Senate is "too close to call," as the polling shows many races within the margin of error and Democrats will have to wait until Election Day to see if polling is right, or if Republicans outperform and remain in control. Midterm elections are commonly viewed as a test of the political environment facing the party in power, and the president's party has historically lost seats during them. Republicans...