WASHINGTON (AP) — Iowa Sen. Chuck Grassley, the longest-serving Republican senator, says he is quarantining after being exposed to the coronavirus. Grassley is 87. He did not say how he was exposed. He said he would follow doctor’s orders and “immediately quarantine” and work virtually as he waits for results of a test. The Iowa Republican is the president pro tempore of the Senate, meaning he presides over the Senate in the absence of Vice President Mike Pence and is third in the line of presidential succession.