The reason ObamaCare will likely devastate many state budgets is massive increases in Medicaid costs.

Heritage blog:

Governors of cash-strapped states are beginning to cajole or bully public employee unions into making concessions on what are considered to be gold-plated retirement and health care packages, which are now collectively underfunded to the tune of $1 trillion.

But as bad as government union contracts and pensions are, they are not the real driver of state insolvency. Medicaid is. Already, Medicaid is the second largest item on the average state budget at 21% (education is first at 22%). But according to the Centers for Medicare and Medicaid Services (CMS) that is all about to change very soon thanks to Obamacare. Remember, more than half of the health care coverage expansion under Obamacare is attained by placing Americans on Medicaid. CMS projects that state and local spending on Medicaid will increase 41.4% between 2010 and 2011. 41%!!! Heritage policy analyst Brian Blaze warns [3]:

If state Medicaid spending increases by 41 percent as projected by CMS, then by next year Medicaid could end up consuming nearly 30 percent of the average state budget. Medicaid would greatly exceed all other state priorities, including education, which tops state budgets at about 22 percent. In fact, state spending on education would experience certain cuts next year.

Presumably, the state spending increase is so high because the enhancement of the federal Medicaid match will expire at the end of 2010. CMS projects that federal spending on Medicaid and the Children's Health Insurance Program will decrease 7.1 percent between 2010 and 2011. The loss of federal funds will drive most of the increase in state Medicaid obligations.