Is a Democratic blue wave inevitable in the U.S.?

According to the polls, the Democrats are poised to take back both the House and the Senate in the upcoming U.S. midterm elections — a prospect that would have seemed improbable a year ago. But the polls have been wrong before. While Donald Trump's approval ratings have hit an all-time low, a lot can change for the Republican Party between now and Nov. 3. Washington correspondents Katie Simpson, Willy Lowry and Paul Hunter take a look at where the midterm races are heating up, what's at stake for Republicans and Democrats, and just how worried Trump might be.