Can a blue wave take down Ted Cruz in Texas?

There probably won't be any surprises in the Senate race there: Incumbent Republican Sen. Ted Cruz and Democrat Rep. Beto O'Rourke are clear favorites to win their respective primaries.

So the bigger question after tonight is whether O'Rourke, who outraised Cruz last quarter and has been aggressively campaigning throughout the state, can ride a blue wave to victory in November.

While O'Rourke certainly has a shot of winning, there are a number of reasons why Democrats should not to get their hopes up.

1. Experts agree Cruz is heavily favored to win

There hasn't been a lot of polling in the race (more on that in a moment), but observers mostly agree that Cruz is "likely" to win. That is, on a scale that goes solid to likely to lean to toss-up, Cruz's chances are more towards the "solid" than the "toss-up". This includes CNN in its race ratings, which has the race as likely Republican.

But just what exactly does likely mean? My old colleague at FiveThirtyEight Nate Silver went back and looked at Senate races since 2010 to see how many times Senate races were won by the side that was "likely" to win in race ratings at this general point in the cycle.

The answer was 85% of the time. Now, saying that Cruz has an 85% chance of winning doesn't mean the race is over. It's approximately equivalent to a person tossing a coin three times in the air and it landing on heads each of those times. I'm sure you've seen that happen many times. Chances are, though, that it won't.

2. The fundamentals suggest Cruz is heavily favored

When there's a general lack of polling, another way of determining the odds on a race is to look at the fundamentals. These include factors such as how the national environment looks (based on the generic ballot), whether the incumbent is running for reelection and the lean of the state on the presidential level (usually measured by examining the last two presidential races).

While the generic ballot heavily favors Democrats, the other two factors don't. Cruz is an incumbent, and incumbents usually receive an added boost. And remember, Donald Trump won Texas by 9, and Mitt Romney won it by 16. In other words, it's still a heavily Republican leaning state as far as we know.

When statistician Dean Strachan looked at these factors back in December, he gave Cruz an 84% chance of winning. That's quite similar to where the expert ratings put the race. A race O'Rourke could win -- though will probably not.

3. The scant polling that does exist favors Cruz

We have not had a non-partisan poll of the race that meets CNN standards in nearly a year. The two surveys that have been released in the past three months have been from a Democratic-leaning outside group and Cruz's own campaign. That doesn't leave us with a lot of confidence in the polling in the race. Still, both surveys had Cruz comfortably ahead -- and the average of the two gave Cruz a 14 percentage point advantage.

Until we get more surveys in the race, it's a little difficult to assess what exactly the polling is saying. Just remember that the January to June polling average before the election in Senate races from 2006 to 2014 had an average error of 6.8 percentage points, and a 14 point lead translates into winning 95% of the time. If the average poll over the next few months looks anything like it does now, O'Rourke's got a long road ahead of him. Of course, maybe O'Rourke closes in on Cruz after his likely win in the primary.

4. The likely voter population leans Republican

A number of analysts have pointed out to Gallup's 2017 polling to argue the race could be close. Gallup had Trump about as unpopular in Texas (approval rating of 39%) as he was nationally.

But as I've noted before, Gallup's polling is of all adults. That's misleading to understanding the electorate in Texas. Trump's approval rating among voters is probably way higher.

Back in the fall of 2016, for example, Marist College polled nine states. They asked about then-President Barack Obama's approval rating. Democrat Obama's net approval rating (approval rating minus disapproval rating) fell by 13 percentage points between the adult and likely voter population. That's more than any other state polled and more than twice the average state.

The reason Republicans do better in Texas among voters is fairly simple. First, the state's voting population is 14 points more white than the adult population, according to the Current Population Survey. Nationally, the average state's voting population is about 7 points more white than the adult population.

Additionally, voting patterns difference between whites and non-whites is greater than it is nationally.

Those two factors make Texas far more Republican leaning than you'd expect looking a poll of all adults.

5. The special election signal

You might think that the special elections so far this cycle are a good sign for O'Rourke. To the degree that they suggest a national environment that leans heavily Democratic, they are.

On the other hand, there's something worrying about the special elections for O'Rourke as well.

The special elections have followed a similar pattern: the 2012 presidential vote baseline has been far more telling than the 2016 presidential vote baseline. If that holds in Texas, it's a big problem for O'Rourke. The reason being that Texas was one of the few states where Democrats did better in 2016 than in 2012, even as the nation became more Republican leaning.

What O'Rourke needs to win is for voting patterns to follow 2016, and then receive an additional boost on top of that. That's certainly plausible. The vote patterns in the 2017 Virginia elections looked a lot more like 2016 than 2012. But even there, Virginia Democratic candidates didn't do that much better than Clinton did in 2016.

Put another way, O'Rourke is going to need pretty much everything to go right in order to win. It can happen, but it's a long shot.