Heading into next year, Democrats will be defending the Senate map from hell.  Twenty-five of the 33 Senate seats up next year’s Senate class are held by the party while Republicans will only be defending eight.

This dangerous over-extension for the party is the result of the 1994 GOP Revolution when the party captured many Clinton voting states (Michigan, Minnesota, Pennsylvania, Maine).  In 2000, these states reverted to the norm and elected Democrats to the Senate.  The class became even more Democratic after the 2006 wave and due to GOP missteps in 2012 the party gained a surprising two additional seats.

Now, the consequences of such success are beginning to show.  Next year, a whopping 10 Democrats will be up for election in states that voted for Trump.  Trump’s appeal in the formerly Democratic leaning Rustbelt has left the party dangerously exposed.  In addition, Democratic successes in Missouri and West Virginia have left their last few Southern statewide elected officials in trouble.

Reflecting the shifting nature of our politics, for the first time in modern elections there was not a single Republican Senate candidate winning a state Clinton won and vice-versa.  While there were certainly cases where Senate candidates outran their party’s Presidential nominee (Missouri, Indiana, New Hampshire) they never were able to get over the top.  The same did not necessarily hold for gubernatorial contests (Vermont, West Virginia, Montana, New Hampshire and North Carolina).

So, should Republicans be banking on this phenomenon to carry them in 2018?  To answer that question we have to look at some examples keeping in mind every state is a little different.  With over a dozen Senate seats considered possibly competitive due to past election results we need to rank them into two categories.  I have done this below.

Now, we are very early in the cycle so this ranking is only a generalistic view of the races based on past history.  Few races have developed to the point of Republicans finding a viable challenger or much polling being done on the contest.  However, past history is a good predictor of the competitiveness of many of these races.

Some of these contests are in perennially battleground states like Florida.  The first five states voted for Trump by double-digits.  Other states like Pennsylvania or Virginia feature a strong Democratic incumbent based on a family’s political history or a trending blue state.

From the above table we can glean the initial competitiveness of these contests.  But, keep in mind many of these states that strongly backed Trump also gave solid margins to statewide Democratic candidates four years earlier.

The polarization of American politics is nothing new but the polarization we saw in 2016 was something unexpected.  But, probably dashing GOP hopes, the reason why it happened is not necessarily because the same set of voters backed Trump and Senate Republicans.

I can think of no two better cases to illustrate this than Pennsylvania and Florida.  In both cases, Trump narrowly won them, but GOP Senators Marco Rubio and Pat Toomey outran Trump in their victories.  In Pennsylvania, the difference manifested itself in Toomey running better in the suburbs and Trump stronger in Western Pennsylvania.  Toomey significantly underperformed Trump in rural areas around Pittsburgh and Northeastern Pennsylvania (Lackawanna, Luzerne).  In Florida, not only did Rubio run ahead of Trump in Southern Florida, but he outright won Pinellas County and ran stronger in Central Florida’s strongest Democratic counties (Orange, Osceola) and urban Jacksonville.

This tends to make the correlation between Presidential results and down-ballot contests seem less deterministic.  When you also consider that there was a wide variation in the results between the Presidential contest and down-ballot races polarization looks even less determinant.

We also need to factor in the unique variables in each states.  Candidates, outside spending, and Presidential popularity all will play a role in these contests.  We cannot even begin to assess these variables this early in the cycle.

Such an analysis should cheer Democrats.  Except for the fact that Trump’s strongest support came in each of the states in the table and that means Trump is unlikely to dip significantly in his support from these states voters.  If Trump is even barely above 50 percent approval nationally Democrats can probably kiss 3-5 of their red state Democratic Senators goodbye considering their lock-step opposition to many of Trump’s policies and cabinet nominees.

On the flip-side, Democrats have some strong incumbents in these states that are well-established, have a history of running ahead of their party’s Presidential ticket (2012) and will be protected by the party establishment.

Still, you can expect Republicans will strongly contest many of these contests regardless.  And in virtually every state they have a deep bench of potential/declared candidates to draw from.