538: The GOP’s Chances Of Holding The Senate Are Following Trump Downhill

[Mr.Phips]

People forget how unpopular both of these candidates are. Trump is such a bad candidate that split-ticket voting will be at record levels by default, like in 1996. Most incumbents simply don't lose by wide margins, unless they're Blanche Lincoln.

In 2008, there was a backlash against pretty much all Republicans and the entire GOP. That is not the case this year.

The electorate was far less polarized in 1996. 

[Mr.Phips]

The only seats that are clearly gone for Republicans right now are NH and WI. We need more polls from IL and IN.

I'd say Illinois too.  Kirk was never gonna win with Presidential year Chicago turnout.

[Mr.Phips]

The one thing most haven't mentioned if it looks like it will be a huge landslide in the Presidency do you start to see voters looking at electing a strong opposition. Remember Clinton despite being well ahead is still not particularly well liked or trusted by a majority of voters. I think you may see an effect where in Atlas blue states like Missouri, Indiana where voters become more interested in keeping Clinton accountable by supporting the Republican candidate. This probably will  be less of a factor in Wisconsin, Illinois, NH, Nevada though and Democratic held Senate seats. Not suggesting it will play a huge roll but I think this could still be in play.

Almost all of the voters thinking this way will likely vote for Trump anyway. 

[Mr.Phips]

The one thing most haven't mentioned if it looks like it will be a huge landslide in the Presidency do you start to see voters looking at electing a strong opposition. Remember Clinton despite being well ahead is still not particularly well liked or trusted by a majority of voters. I think you may see an effect where in Atlas blue states like Missouri, Indiana where voters become more interested in keeping Clinton accountable by supporting the Republican candidate. This probably will  be less of a factor in Wisconsin, Illinois, NH, Nevada though and Democratic held Senate seats. Not suggesting it will play a huge roll but I think this could still be in play.

Almost all of the voters thinking this way will likely vote for Trump anyway. 

The voters most likely to take that stance are independents, and right now I don't think Trump is winning them.

Independents have recently voted for the same party down ballot as they do for President, which is why Senate races and the House vote have closely tracked that of the Presidential race since 2000.  This isn't like the 1970s and 1980s when you had reliably Democratic voters switch to vote for Nixon and Reagan at the top of the ticket.