A SurveyUSA was a robopoll taken on 678 likely voters (3.8 MOE) from 24-27 October and has Rossi and Murray tied up at 47% each. The KCTS/KPLU/Washington Poll poll used live interviews of 500 registered voters (4.3 MOE) taken from 18-28 October, and has Murray leading 49% to 45%.
In some sense, both of these polls are older than yesterday’s Rasmussen robopoll of 750 likely voters (4.0 MOE) taken completely on the 26th of October that has Rossi up +1% (48% to 47%). Therefore, the only reasonable thing to do is combine all three polls into one meta-poll and do a Monte Carlo analysis.
The combined 1,928 “votes” are split 916 for Murray (47.5%), 904 for Rossi (46.9%) and 108 (5.6%) for neither candidate. From a million simulated elections at these proportions and sizes, we learn that Murray wins 579,294 times and Rossi wins 414,495 times. In sum, these three most recent polls support a Murray victory with a 58.3% probability and a Rossi win with a 41.7% probability. This is very close to a tie (statistically, it is a tie), but Murray has a slight edge.
The resulting meta-poll has a total of 5,140 “votes,” of which 2,484 go to Murray (48.3%), 2,406 go to Rossi (46.8%), and 250 go away. From a million simulated elections, Murray wins 785,190 times and Rossi wins 211,969 times. Thus, from the evidence found in polls taken over the past two weeks, we find that Murray has a 78.7% probability of winning and Rossi has a 21.3% probability of winning.
Statistically, the race is a tie because the probability of winning is under 95%, but the odds do favor Murray a little bit.