Mississippi runoff: What we learned from 2018's last Senate race

Yet, Hyde-Smith's win and the (relatively small) size of it makes a lot of sense when put in the context of this election cycle. Here are five takeaways for the Mississippi race and why it went down the way it did.

1. The result looked like what you expect in a blue wave climate

Mississippi is a really red state. President Donald Trump won it by 18 points in 2016. Therefore in a political environment in which Democrats are winning the national vote by high single digits, we wouldn't expect a Democrat to win a Senate seat in Mississippi. Rather, we'd expect them to come closer than Hillary Clinton did in 2016. That's exactly what happened.

When I used the results of other Senate races this year and controlled for incumbency and past presidential vote, a Hyde-Smith win of about 7 percentage points was predicted. That's right around the margin she ended up winning by.

2. Hyde-Smith's comments probably hurt her

Back in the primary when all the Democrats and Republicans ran against each other, the Republicans combined for 58% of the vote to the Democrats 42% of the vote. In our hyper-polarized political climate, you'd expect Hyde-Smith to capture pretty much all of the other Republican votes. Remember her Republican opponent in round one was the even more conservative Chris McDaniel, whose voters would not be inclined to vote for Espy.

Instead, Espy gained about 5 points in the runoff relative to his primary vote share of 41%. His performance in the state looks to be better than any Democratic Senate candidate in 30 years.

3. Trump helped Republicans in 2018 Senate races

It's not entirely clear whether Trump's last minute visit to Mississippi made any difference. What did help Hyde-Smith though is that Trump is well liked in the state.

An RRH Elections live interview poll that called landlines and cell-phones taken before the runoff had Trump's approval rating at 56% among runoff voters. (A Marist College poll last month had his approval rating at 56% among all voters.) Hyde-Smith, who tied herself very closely to the president, was winning pretty much all of those approvers. Tonight's results bear out that polling.

Put into the larger Senate picture, Republicans did well in solid red states. They were able to pick up a net gain of two seats in 2018 in part because there were five Democratic incumbents running in states Trump won by 19 points or more in 2016. Republicans won three of those five seats. They also held onto the two Republican seats that were thought to be at least vaguely competitive (Mississippi and Tennessee) in states that were about as red.

4. Democrats future hopes are among college educated voters in non-rural areas

The big story of election 2018 was how Democrats were able to win over traditionally Republican-leaning college educated voters. The exit polls reveal they won them by a 20 point margin in the 2018 House vote.

Mississippi was exactly the wrong place to see that in action. The state ranks 49th in the country for adults with a college degree.

Additionally, Democrats did very well in cleaning up in urban and suburban areas. For instance, there's not a single Republican representative in a congressional district that is completely urban.

Mississippi, though, ranks in the top 5 for population living in a rural area.

5. Doug Jones' Alabama victory happened in a unique circumstance

A lot of Democrats had hoped that deep red state Mississippi would turn out like deep red state Alabama after Hyde-Smith got herself into hot water.

Jones' opponent, Roy Moore, was disliked coming into the election. He considerably underperformed in his prior statewide race for state supreme court. Hyde-Smith won 61% of the vote in her prior statewide race for Commissioner of Agriculture and Commerce. The accusations of sexual misconduct against Moore were the final straw, while Hyde-Smith had room to spare.

Perhaps as importantly, Trump's approval rating nationally was about 6 points lower during the Alabama election than it is now.

That's why we'll have to keep an eye on it heading into 2020. If his approval rating is where it is now, Republicans will suffer, though they won't lose in deep red areas. If it drops, a Trump defeat won't just bring him down, it could bring Republicans down even in the Deep South.