In Saturday’s Republican elections, Ted Cruz outperformed his pre-election polls in all three states where data was available: Kentucky, Louisiana, and Kansas. This is in contrast with Donald Trump, who performed within 1-2 percentage points in Kentucky and Louisiana…but underperformed by a remarkable 12 percentage points in Kansas. What’s going on?
Looking at the graph above, Cruz has always outperformed his polls – in 17 out of 18 states so far. The higher he is positioned in polls, the bigger the effect – and this weekend’s states were good ones for him to begin with. Overall, his eventual vote share is typically 1.3 times higher than his pre-election polls. That is a considerable difference.
It has been said that Cruz benefits from caucuses and closed elections in which independents cannot vote. However, when these features are present, he also runs stronger in polls. Overall we have three correlated variables – Cruz support, closed primaries, and caucuses – and so it is hard to say what is causative. One way to restate the phenomenon is to say that Cruz voters are almost 1.3 times more likely to vote than other voters (Trump, Rubio, and Kasich supporters) whom pollsters reach. Cruz voters are a dedicated lot.
The tendency for pollsters to undercount his supporters may affect estimates of what will happen in elections from now to March 15th, most of which are closed and/or caucuses.
That brings us to Marco Rubio. His home state of Florida’s primary is closed. The last three surveys (2/24-3/2) give a median of Trump 45%, Rubio 25%, and Cruz 15%. However, this weekend, Rubio underperformed by 6 percentage points in Kentucky, and by 4 percentage points in Louisiana. It seems that Rubio’s attempt to use Trump’s highly personal attack style has not worked well for him. Combined with Cruz’s tendency to overperform, there is some chance that Rubio will end up in third place in his own state.