House effects show how each pollster compares to the cross-pollster average. A positive (red) value means the pollster tends to put that party higher than average; negative (green) means lower.

Methodology: For each pollster, we calculate their average vote share per party. The overall average is the mean of these pollster averages, giving equal weight to each pollster regardless of how often they poll (so a pollster publishing daily doesn't skew the baseline). House effect = pollster average minus overall average. Only pollsters with 5+ polls in the selected window are shown.