JEFF GREENFIELD:

Well the first thing is that just a president's party almost always loses seats in a midterm election. There have been like two exceptions in the last two years. Second a party's prospects are generally linked to their president's approval ratings currently trumps average approval rating this past month is about two points lower than Obama in 2010 when Democrats suffered a disastrous midterm. But there are specific problems this time for Republicans. First some 40 Republican incumbents are leaving while only 18 Democrats have announced their retirements. And it's just easier to flip an open seat. Second 25 House Republicans are in districts carried by Hillary Clinton. Two years ago mainly in suburban districts literally from coast to coast. Only 13 Democratic seats are in Trump friendly districts. And it is here in suburban America where the president's approval ratings are particularly low. Third unlike the last midterms when Republicans were on the offensive on issues like Obamacare this time voters are concerned about threats to health care and the GOP signature issue, those tax cuts, are actually meeting with disapproval. So right now with 42 Republican House seats in danger and only three Democratic seats in danger oddsmakers say there's a 4 to 1 chance that the Democrats will win the necessary 23 seats to get control of the House. Let's remember however that Hillary Clinton was a 3 to 1 favorite on Election Day two years ago. Let's talk about the Senate the Senate is completely different. The map for 2018 is nothing less than a nightmare for the Democrats. Only one Republican seat is in a state Clinton carried. That's Nevada. But 10 Democratic incumbents are running in states that Trump carried five of them by landslides. And in those states Trump's approval ratings are better than his national average right now. Democratic senators are facing serious challenges in Florida, Indiana, Missouri, North Dakota, Montana. GOP seats are vulnerable in Arizona, Nevada, Tennessee and maybe Texas. Democrats need a net gain of two Senate seats to take control of that chamber. It's in the red states where the Kavanaugh nomination may play out particularly influentially. Remember only senators not congressmen not House members vote on confirmation. The feeling was that these red state Democrats might be pushed to vote for confirming Kavanugh – the recent allegations may make that differently. Also in these states centrist Democrats are going to be pushed by their Republican opponents on immigration and on whether they embrace the policies of the more progressive left swing of the National Democratic Party.