THE REAGAN revolution has thus far met with nothing like an organized opposition. A politically powerful one may now be forming among the ranks of governors and mayors. Having led the fight for a stronger role in the nation's affairs, these officials are now finding that the first round of the budget fight has left them with less money to do more work.

President Reagan thinks that the governors and mayors are ungrateful. Yes, they took some big cuts, but look at the 300-plus pages of federal regulations that his administration has eliminated. This will free up states and localities to use their remaining money more wisely and prepare for more cuts.

When states and localities have had time to understand the streamlined rules, they certainly should be pleased. Essentially the new regulations --governing seven of the nine block grants into which more than 50 programs were consolidated-- tell them to look at the programs' statutes and figure out for themselves what Congress intended. No more annual plans to perform the impossible, no more strict requirements for serving particular groups, no more periodic performance reports.

Of course statutory limits will still apply, and some of the block grant laws have a lot more strings than the states would like--particularly requirements for maintaining the shares spent on certain activities and projects. Prudent states will also want to set guidelines and monitoring procedures of their own, and, presumably, the federal government will still want to have some way to tell if the money is spent in the ways intended--which wasn't always the case in earlier experiments with block grants.

Still progress toward simplification has been made and more is likely to follow. What is really bothering the mayors and governors is a growing fear that another round of hasty federal cuts will result in an unhealthy and politically unsupportable concentration of unpopular responsibilities at their levels of government. This fear is prompting loud calls for sorting out and balancing federal, state and local responsibilities before any more shifts are made.

Concern is particularly acute at the state level, where responsibility for society's outcasts--the poor, sick, handicapped and criminal--are already concentrated. Many states have, in recent years, taken over much or all of local government's share of welfare and medical aid for the needy. They have done this because local tax resources can't expand to cover increased need caused by population shifts or local job losses. But states, too, have difficulty raising taxes to meet new needs, especially if state taxpayers feel that a substantial part of state taxes is already going to people unlike themselves. All of this makes a strong case for what the states now want--a larger assumption by the federal government of the costs of providing basic income, food and medical assistance in return for any additional state assumption of costs in other areas like education and transportation.

This is a fair demand. And since it is being made by governors and mayors from all areas of the country and all parts of the political spectrum, it is one that the administration and Congress cannot afford to ignore.