(CNN) Democrats are favored over the Republicans by a 54% to 38% margin in CNN's new congressional ballot poll. This 16 point Democratic lead is up significantly from 5 points last month and it is in line with a Democratic advantage of 18 points in December. Although CNN polls have bounced around they share something in common that should worry congressional Republicans: voters are viewing their midterm choices based upon how they feel about Republican President Donald Trump.
The latest CNN poll finds that Democrats lead by an astounding 88% to 7% margin among voters who disapprove of the job Trump is doing as president. That 81 point margin is mostly in line with the 75 percentage point and 76 percentage point lead Democrats held in January and December, respectively.
Republicans, for their part, are winning over most voters who approve of Trump's job performance. The latest survey has them up by a 71 point margin, while January's and December's surveys had them up by 81 points and 78 points. All told, the average of the three polls have congressional Republicans up by 77 points among Trump approvers, which is identical to the 77 points congressional Democrats lead by among Trump disapprovers.
This may seem good for Republicans, but it's a big problem because Trump is far more disliked than he is liked. The latest CNN poll has his disapproval rating among voters at 17 percentage points below his approval rating (a net approval rating of -17 points). An average of the last three CNN polls also puts him at a net approval rating of -17 percentage points among voters, which is similar to other polls.
If Trump's net approval rating among voters on Election Day is -17 points, Republicans have got to win by a significantly wider margin among Trump approvers than Democrats do among disapprovers. Even if Republicans win Trump approvers by 12 points more than Democrats win among Trump disapprovers, Democrats would still be projected to win the national House popular vote by 7 points. That margin gives Democrats no worse than a 50% chance of winning a majority of House seats.
It should be noted that House Republicans pulled off this task in 2016. Back then, Trump was quite unpopular with a favorable rating of 38% to an unfavorable rating of 61% in the exit polls. House Republicans were able to overcome that by winning among those who had an favorable view of Trump by 84 percentage points and only losing among those who had an unfavorable view of Trump by 50 points.
The key difference this year, as I have pointed out before, is that 2018 is a midterm election and 2016 was a presidential year election. Hillary Clinton is not on the ballot, and Republicans did very well among those who disliked both Clinton and Trump.
Since 1982, there has never been a midterm election in which the president's party has won by significantly more among approvers of the President than the opposition party has won by among disapprovers of the President.
In fact, the President's party has tended to do worse among approvers of the President than the opposition party has done among disapprovers. Now, the last few election cycles have shown an evening out in how well each party does with their bases. In the median election since 1994, the President's party has only done two points worse among approvers than the opposition party has done among disapprovers. In no election, however, has the president's party won among approvers by 7 points more than the opposition party has won among disapprovers. The gap in 2018 would need to be nearly double this all-time high for Republicans to hold the House given Trump's popularity right now.
That's why it's going to be important to continue to watch the President's approval rating over the next few months. The polling suggests that his popularity and the midterm fate of House Republicans are linked. If previous trends hold (and they don't always) and Trump continues to be this unpopular, Republicans, simply put, have very little chance holding the House.