Examining survey data carried out from 1972 to 2000 Karen Stenner (The Authoritarian Dynamic, pp. 189-92) suggested that over this 29 year period Americans have become more "intolerant." This racial, political and moral intolerance has not been primarily due to 'conservatism' but to 'authoritarianism.' Stenner wrote (p. 191): "Authoritarianism is the primary determinant of general intolerance of difference in the contemporary United States, and it becomes increasingly powerful over time.... Authoritarianism alone can explain a quarter of the variance in all intolerance of difference in [1972-82], and very nearly half the variance in [1990-2000].... Both the explanatory power and impact of conservatism are far more modest, and they generally diminish from the earlier to the later period, as the traditions conservatives are dedicated to conserving grow increasingly tolerant."
This suggests that what was growing in the United States over the 1972-2000 period was not the expression of 'conservatism'; rather it was the expression of racial, political and moral intolerance that was increasing, i.e., authoritarianism.
Although "punitiveness" plays a role in authoritarianism, as a sidelight it is interesting to note that it apparently played no significant role in accounting for intolerance during this period. Why? Stenner wrote (p. 191): "The United States is one of the most extraordinarily punitive nations, by every indicator, and by any comparison, not limited to liberal democracies or 'advanced' economies. This exceptional punitiveness includes, among other things, the proportion of the population imprisoned or otherwise in the 'care' of the criminal justice system; the severity of sentencing for minor crimes; and support for, imposition and execution of the death penalty [sources provided].... Since there is nothing the least bit abnormal about extreme punitiveness in the United States, then or now, we cannot expect authoritarianism to exercise much influence in regulating intolerant responses in that domain, then or now." In other words, if we're trying to explain variation in intolerant views over time, then a potential contributor that doesn't vary much (punitiveness) isn't likely to help.
Stenner (pp. 192-95) also examined the comparative influence of conservatism vs. authoritarianism upon the variation in racially intolerant views in both 1972 and 1996. She found that whereas conservatism explained some racial intolerance in 1972, given the generally increasing racial tolerance over 1972-96, conservatism accounted for very little racial intolerance in 1996. However, at both points in time authoritarianism accounted for a good deal of the variation in racial intolerance.
Bottom line: It is absolutely critical for accurate understanding of the U.S. political landscape to carefully differentiate conservatism from pseudo-conservative authoritarianism.