Forty-seven percent of 800 respondents said they opposed the ban, while 39 percent said they supported it. If the law had included an exception for rape and incest, the poll found, 59 percent would have favored it, with 29 percent opposed.
Only one clinic in the state provides abortions. In all likelihood, relatively few of the 814 abortions performed in South Dakota in 2004, for example, involved either rape or incest. Statistics cited at Wikipedia put the number of abortions conducted for that reason at 1%-2.1% of the total, about 8-17 abortions a year in South Dakota.* In all the bill would allow about 40 abortions a year in South Dakota, if enforced. But, for about 20% of voters, the distinction is a crucial one, and it makes the difference between passage and failure of the measure politically.
The Washington Post rightly notes that South Dakota "twice gave George W. Bush 60 percent of the vote," and the Republican Governor signed the bill.
In the state House, where HB 1215 was approved 50 to 18, the primary sponsor was [Roger W.] Hunt, a Republican. In the state Senate, where the vote was 23 to 12, the chief sponsor was Julie Bartling, a Democrat.
The fact that a bill with such overwhelming support among elected officials may have a tough time passing muster with the voters in this very conservative state, on a high profile issue (nobody was unaware of what they were voting on in the case of this bill) shows just how crude an instrument representative Democracy can be, although the distinction may also be a function of the intensity of voter preferences on abortion further modified by a stronger legislator graps of the unlikelihood that the bill will actually become law than the average voter.
* The Wikipedia numbers on why women choose to have abortions are highly relevant to the abortion debate, so I'll provide the full list here:
25.5% Want to postpone childbearing
21.3% Cannot afford a baby
14.1% Has relationship problem or partner does not want pregnancy
12.2% Too young; parent(s) or other(s) object to pregnancy
10.8% Having a child will disrupt education or job
7.9% Want no (more) children
3.3% Risk to fetal health
2.8% Risk to maternal health
2.1% Rape, Incest, Other
You can check their source here. The sample size is 1,773. It further notes that:
In the United States and in some Eastern European countries for which data are available, about one-half to three-fifths of all pregnancies are unintended, and a large proportion of these are resolved through abortion.
It also notes that in Mexico, which has an abortion law similar to that being considered by voters in South Dakota (but with a rape exception) that 43% of unintended pregnancies are resolved by abortion.