Here is an interesting summary of the defense in Clinton's trial in the Senate (from Wikipedia):
"Clinton's defense counsel argued that Clinton's grand jury testimony had too many inconsistencies to be a clear case of perjury, that the investigation and impeachment had been tainted by partisan political bias, that the President's approval rating of more than 70 percent indicated his ability to govern had not been impaired by the scandal, and that the managers had ultimately presented "an unsubstantiated, circumstantial case that does not meet the constitutional standard to remove the President from office"
They cited partisan bias and approval ratings!
"Clinton's defense counsel argued that Clinton's grand jury testimony had too many inconsistencies to be a clear case of perjury, that the investigation and impeachment had been tainted by partisan political bias, that the President's approval rating of more than 70 percent indicated his ability to govern had not been impaired by the scandal, and that the managers had ultimately presented "an unsubstantiated, circumstantial case that does not meet the constitutional standard to remove the President from office"
They cited partisan bias and approval ratings!