Today on Midday on Politics, we assess the state of Senate races around the country, in light of the death on Friday of Supreme Court Justice Ruth Bader Ginsburg. How will her passing and the fight over her successor affect the composition of the United States Senate, and the 2020 presidential election? Twenty-one Republican incumbent senators are on the ballot. There are three open seats currently held by Republicans. Eleven Democratic incumbents face re-election. There’s one open seat currently held by a Democrat, in New Mexico. If Democrats win three or four seats currently held by the GOP, they will take control of the upper chamber. Two Democrats, Doug Jones of Alabama and Gary Peters of Michigan are considered vulnerable, and if they lose, the magic number for Democrats is possibly higher. Some polls suggest that Republicans in North Carolina, South Carolina, Colorado, Montana, Iowa, and elsewhere could be displaced come November. Tom's two guests today help us take a closer look at these battleground contests for Senate control, and understand how the outcomes may be influenced by the epic Senate battle ahead over the new vacancy on the Supreme Court. Fred Hill joins Tom first, on Zoom, from his home in Arrowsic, Maine. He is a former reporter, foreign correspondent, bureau chief and editorial writer for the Baltimore Sun. In the 1980s, he served as an aide to Maryland Sen. Charles “Mac” Mathias before moving to the State Department, where he served until 2006. His latest book is called Dereliction of Duty: The Failed Presidency of Donald John Trump… Fred Hill has been closely watching the contest in Maine between longtime incumbent Republican Sen. Susan Collins and her Democratic opponent, Maine's House Speaker Sara Gideon. Later in the hour, Tom is joined on the line by Susan Davis, NPR’s congressional correspondent and co-host of the NPR Politics Podcast. She and Tom discuss the Justice Ginsburg factor in the country's already deeply polarized election season, and they spotlight some of the other key battleground election contests across the country that promise to change the balance of power in the US Senate.