The Odds Against O'Rourke: Some Back-of-the-Envelope Vote Counting in the Texas Senate Race

A series of recent articles focused on Republican concerns over Senator Ted Cruz's reelection chances has Democrats beaming, and national reporters falling all over themselves to get in front of the possible defeat of Cruz in deep red Texas. The attraction of the storyline for editors and reporters is obvious enough, and poll numbers showing low single-digit leads for Cruz provide a ready rationale for ever more breathless speculation on Beto O'Rourke's chances of pulling off an upset. But a look at recent election outcomes and some simple back-of-the-envelope math highlight just how unlikely an O'Rourke victory is in Texas.

While "unlikely" doesn't mean impossible – this is where we usually insert something about a "non-zero probabability" – the magnitude of the change in the patterns evident in recent Texas elections would have to be historic. If we consider recent midterm elections since 2010, the average Republican vote total has been 2,798,519 votes, which we can round to 2.8 million for simplicity. The average Democratic vote total in those races has been 1,846,459, which we can round up to 1.9 million (again, for simplicity). This means that Democrats, on average, have to make up approximately 900,000 votes to get in the range of a tie in Texas. What would this take? (The table below also includes presidential results from 2016, just to provide context, though those results are not factored into these averages).

Recent Top of the Ticket Election Outcomes in Texas
Year Race Republican Vote Total Democratic Vote Total Republican Vote Total Advantage Republican Vote Share Advantage
2016 President 4,685,047 3,877,868 807,179 +9
2014 Senator 2,861,531 1,597,387 1,264,144 +27
2014 Governor 2,796,547 1,835,596 960,951 +20
2012 President 4,569,843 3,308,124 1,261,719 +16
2012 Senator 4,440,137 3,194,927 1,245,210 +16
2010 Governor 2,737,481 2,106,395 631,086 +13

This assessment is based on some quick math, rather than finely grained projections, geographic or otherwise, and there are plenty of other ways one might go about this exercise. But simply thinking about vote totals based on previous elections provides a succinct look at what one is talking about when one considers Beto O'Rourke defeating Ted Cruz.

A good starting point is one of the underlying assumption of many assessments of O'Rourke's chances: the potential migration of votes from the expected GOP vote either to O'Rourke or to the Texas army of the non-voting. The most recently released poll, as of this writing, showed 15 percent of likely Republican voters saying that they'll cast a vote for O'Rourke. According to a few different analytic approaches using University of Texas / Texas Tribune polling data of registered voters, as well as Texas Lyceum data of registered and likely voters, the size of the poll of potential Republican cross-over voters is probably closer to 6 percent. This estimate is drawn from current polling, which almost certainly reflects a different underlying population than the likely electorate once general election voting begins, so the size and magnitude of the shift in this data may or may not emerge in actual voting. But assuming just for the sake of this exercise that O'Rourke has or will convince 15 percent of Republican voters to cast a vote for him (which would be quite impressive), we can subtract those votes from the average Republican vote total and add them to the average Democratic vote total, resulting in 420,000 votes shifting to the O'Rourke column. This would cut his likely deficit to 480,000 votes.* While this 15 percent estimate seems high given the context (and divergence of) the polling data, it tests the outer limits for one of the clear concerns of Republicans in Texas and elsewhere: the possibility of either a lack of enthusiasm or outright discontent leading to an increase in Republican non-voting among usually reliable midterm voters.

In addition to discontent with Cruz amongst Republicans, O'Rourke would also have to turn out Democrats at significantly higher rates than normal. So let's assume, again for the sake of argument, that Democratic turnout increases by 20 percent, which would add another 380,000 votes to O'Rourke's total. Even under this optimistic scenario, combined with the outer-bound estimate of Republican defections, this surge in turnout would only result in a decrease in the overall expected gap between O'Rourke and Cruz to 100,000 votes – a little more than 3.5 percent under our rough turnout assumption – still in Cruz's favor. 

This simple, back-of-the-envelope calculation using incredibly optimistic expectations (if you're a Democrat) about the electorate shows why, when experts are asked about O'Rourke's chances at toppling Cruz, they are so cautious in feeding the hype. Even under extremely rosy circumstances, O'Rourke needs BOTH a momentous shift in voter sentiment, AND a momentous shift in Democratic turnout: possible, but still not probable.

* This is, by design, a tough test for Cruz, since we're not only assuming that Cruz loses 15 percent of his expected vote total, but that it all goes to O'Rourke. A more reasonable possibility would be some degree of demobilization, which removes votes from Cruz without adding to O'Rourke's total. While speculating on this could be interesting, in the end, in this exercise, we're not interested in figuring out the lower-bound of O'Rourke's appeal, but the upper bound. Additionally, the difference in vote totals for Republican candidates in the three most recent, top-of-the-ticket, midterm elections is only 124,050 votes, or 4.4 percent of the 2.8 million GOP baseline that we're using in this quick analysis – highlighting the actual magnitude of a 15 percent shift in either turnout or sentiment.