Paying for Pre-K
One of the big questions about pre-k expansion proposals is how to pay for them. I'd posit that the Congressional Budget Office's just-released Summary Table of Options for Reducing the Deficit might be a good place to look for potential savings with which to fund pre-k investments.
I'd also suggest that this is one instance where the "pre-k produces savings that can help pay for pre-k investments" argument has some real merit. While research does suggest that high-quality pre-k eventually produces reductions in public costs (for special ed, grade retention, welfare, and incarceration) and increases in revenues (from both increased earnings today for mothers who can work more due to reliable childcare provided by pre-k, as well as increased earnings for pre-k grads as adults), the notion that these savings can be used to "pay for" pre-k is generally suspect because: a) most of those savings/increased revenues occur in the future, while pre-k costs must be paid today, and b) savings or increased revenues produced by pre-k are extremenly diffuse, making it difficult in practical terms to capture them to "pay for" pre-k. But both these issues are less problematic if one is considering a trade-off between pre-k spending and deficit reduction, because a) the primary causes for concern about the deficit are not today, but in medium- to long-term future, exactly when pre-k investments made now should be producing benefits, and b) the types of diffuse broad public benefits that pre-k generates actually should help reduce future deficits, by increasing economic growth, boosting revenue, and reducing a variety of public costs.