try " Republican ... mean-spirited " versus "Democrat ... mean-spirited" and also other 'harsh' adjectives close to Repub or Dem ("extremist" or "harsh" or "hard-line" or "controlled" or "regime" or "forced" or "threatened").
on the "threatened" for example, i have notice the NYT/LibPress would say "Clinton promises veto" but would say "Bush threatens veto". So you may get: "Extremist Republicans, taking a hard line, threatened to overturn LovelyDemPres promised veto."
Here are the number of times these things appear (in the NYT national desk news pages):
Democrats Promise: 2
Republicans Promise: 39
Democrats threaten: 3
Republicans threaten: 6
Every time I look for bias, I don't always find conclusive results...
Here are the number of times these things appear (in the NYT national desk news pages):
Democrats w/10 mean-spi!: 22
Republicans w/10 mean-spi!: 40
This is also not proof of media bias, because these might just be quotes from the article--the NYT isn't guilty of bias just because it quotes a shrill harpy left-wing activist and a reasonable-sounding conservative activist. Also, this just means the words are in proximity, it doesn't necessarily mean they describe each other (for instance, "Democrats say mean-spirited conservatives are..." would show up under "democrats w/10 mean-spi!" It's important to remember the limitations of this method.