On what issue is the gap between liberals and conservatives widest?

When reading about politics outside of the US, I have to be wary of the presumption that descriptors such as "liberal" or "conservative" have the same connotations there as they do here. It's a two way street, of course, so the following may be of use to readers outside America.

But it also has utility for those in the states. I was recently in a discussion where the topic of what issue most starkly divided liberals from conservatives came up. I guessed that it was either abortion or taxes, but had to admit to being uncertain. Without any false modesty, as it turns out.

The following table shows the differences among self-described liberals, moderates, and conservatives on several different political issues, as well as a few broad lifestyle measures. The fifth column shows the difference between liberals and conservatives by subtracting the percentage of conservatives in agreement from the percentages of liberals in agreement. For consistency, the items are measured in a way that affirmation of the statement represents what is conventionally thought to be the liberal position. For contemporary relevance, all responses are from 2000 onward:

	Lib	Mod	Con	Dif
Same-sex marriage should be legalized	61.8	36.9	19.9	41.9
Homosexual relations are morally acceptable	51.6	32.3	18.6	33.0
Abortion should be legal in all circumstances	57.3	40.4	27.3	30.0
Gov't should definitely provide healthcare for the sick	69.1	56.2	41.0	28.1
Man evolved from other animals	66.2	51.7	39.2	27.0
No belief in or uncertainty over existence of God	53.4	35.7	28.2	25.2
Military spending is too high	42.4	21.9	17.4	25.0
Marijuana usage should be legalized	50.3	35.1	25.7	24.6
Taxes on the rich are too low	55.6	52.5	33.0	22.6
Attend religious services less than once a month	63.8	56.4	41.8	22.0
Assisted suicide allowed for those with terminal illnesses	72.5	60.8	51.1	21.4
Outlaw capital punishment for murderers	44.0	29.7	22.7	21.3
Prayer in public schools should be banned	54.2	37.8	34.2	20.0
Gov't has an obligation to help blacks specifically	28.4	15.9	10.3	18.1
Have never been married	34.1	22.9	18.3	15.8
Police permits should be required for gun ownership	86.9	82.0	73.8	13.1
Affirmative action for blacks does not hurt whites	40.2	32.2	30.8	9.4
Immigrants pose no threat to English language	71.3	68.6	62.0	9.3
Hispanic immigration should not be decreased	63.1	52.1	56.0	7.1
Science does more good than harm	62.6	57.1	61.0	1.6

Same-sex marriage (and gay issues in general) trumps abortion in divisiveness. That gay marriage, abortion, defense spending, evolution, healthcare spending, and belief in God are the most polarizing issues in contemporary US society while affirmative action, immigration restrictionism, and government largess for blacks are far less firmly associated with political orientation is discouraging (though not surprising) from my particular vantage point, as someone who identifies in the vernacular as a conservative (and an "empirical paleoconservative" in situations where such phraseology won't be met with annoyance and/or confusion). The things I, alongside many others in the Steveosphere, find most important are not the things mainstream conservatives differ from the left on the most.

On theism, military spending, prayer in public schools, and affirmative action, moderates and conservatives are well aligned, while on the taxing of the rich, moderates and liberals are on the same page. Liberals are significantly less likely to believe in God or have ever been married than moderates or conservatives. On everything else (excepting the last two, for which political orientation has little relevance), moderates fall roughly halfway between liberals and conservatives.

Parenthetically, the GSS is weak on items relating to immigration. A question much preferable to the vague and loaded one about English being threatened by immigrants (xenophobes always feel threatened by the "other"!) would be one that simply asks whether immigration to the US should be increased or decreased, but such a question has not been asked. The closest we get is a set of questions posed in 2000 asking alternatively whether Hispanic, Asian, and European immigration should be increased, left the same, or decreased. While sentiment is generally restrictionist regarding immigration into the US (especially illegal immigration), whenever immigrants are defined anymore specifically than simply being aspiring immigrants, that restrictionism shows itself to be pretty thin. Immigration has nothing to do with biology or even culture, it's about the rule of law!

GSS variables used: ABANY, GRASS, HOMOSEX, PRAYER, HELPBLK, DISCAFF, MARHOMO, GUNLAW, TAXRICH, CAPPUN, ENGTHRTN, GOD, ATTEND, SUICIDE1, HARMGOOD, EVOLVED, MARITAL, SPARMS, LETINHSP, HLTHCARE, YEAR(2000-2008), POLVIEWS(1-3)(4)(5-7)