A further note on S+W Benchmark Accuracy
Close followers of the 2020 presidential primaries will recall after Joe Biden’s big win in South Carolina on Feb. 29 that Tom Steyer, Pete Buttigieg and Amy Klobuchar all dropped out before the March 3 California Primary and other Super Tuesday contests.
Although all three remained on the California ballot, a fair question is whether these drop-outs may have benefited either Bernie Sanders and Elizabeth Warren and thus skewed the S+W Benchmark figure as a reliable Progressive barometer.
After a review of the polling data, it appears the only major candidate to benefit from the drop-outs was Biden. The strongest evidence comes from the last major polls of California voters before the seismic shift caused by Biden’s 29-point South Carolina landslide. These polls were conducted by CNN, YouGov, Suffolk and UC Berkeley of California primary voters.
Averaged, these polls predicted a 17-point winning margin for Sanders in California, with an average S+W of 49%. On election day, that S+W stayed fixed (49.2%), but Sanders’ victory margin narrowed to 8 points as Biden surged from an average of 12.5% in those four polls to 28% on election day. This suggests most late-changing votes shifted to Biden (and perhaps to Michael Bloomberg).