To Speak the Truth to Power can be applied today to those in the people's House, the House of Representatives, who are speaking the truth to "the powers that be" in the more senior Senate and in the Executive branch of government. Regardless of which political party controls these branches of government, after an election in which control of the House changes parties, and when the Senate and/or the White House are in the control of the other party, truly the new members of the House can Speak the Truth to Power. Many sayings originate in one group and spread to the general public, from jazz, a movie line, etc. While this saying may have originated with liberals, it probably originated when liberals were in the minority. The more salient feature is not whether the speaker of the saying is liberal or conservative, but whether (s)he is in power or not.
Health review leader promises to ‘speak the truth to power’
... the review was a chance to ‘pause, listen, reflect and improve’ on the proposals before they were passed back to the House of Lords in June ... I come from a sector that speaks truth to power. So people can be assured when they’re making comments to us we will listen to what they say’ (Sir Stephen Bubb).