JUST IN TIME to cushion the blow of new real-estate tax assessments, Mayor Washington has proposed a program that would ease the city homeowners' tax burden. Not surprisingly, political observers in city hall (which means the mayor's opponents and their supporters) see the announcement as politically motivated. So what? If it takes an election year to motivate the mayor on this score, then there's something to be said for local politics. And, as City Council member Marion Barry Jr. has said of Mayor Washington's move, "I'm glad to see he's got religion. His proposal is just a refined version of my own."

It is. Moreover, as the mayor has duly noted, it would be politically "perilous" for the council to reject or substantially change this proposal. Rocketing property assessments over the years have produced enormous jumps in homeowners' tax bills - to the point where many people feel they are priced out of living in homes they may have bought years ago at low cost. Just in the past year, tax assessments on single-family homes in the city have increased an average of 19.7 percent - reflecting an average market value of $44,837 for the estimated 100,000 single-family dwellings. At this year's real-estate tax rate, the next bill on this $44,837 would be $135 more than last year's.

Mayor Washington's measures would just about eliminate tax increases for homeowners, while permitting the bills to rise on commercial and rental properties. So instead of a $711 bill on that average $44,837 home, the bill would be $563, which would be $13 less than it was last year. The current tax rate of $1.83 for each $100 of assessed valuation would drop to $1.57, effective July 1. In addition, the mayor is proposing an increase in the "homestead exemption" on each owner-occupied dwelling, from $6,000 to $9,000. This is the amount you subtract from your assessment value before applying the tax rate on your home. At the reduced rate, this change in itself would mean a $141.30 cut for every homeowner.

Owners of rental or commercial properties aren't going to be among those hailing the tax proposals, however, for their rates would stay at $1.83. But this differential rate is consistent with the recommendation recently by a city tax revision commission - and has already been proposed in a city council bill introduced by Mr. Barry. In proposing these changes, Mayor Washington notes that other sources of city revenue, such as the income tax and sales tax, also have been rising. As a result, the mayor has an additional proposal for income tax credit for low-income residents.

Though it remains to be seen how well the mayor's fiscal reshuffling will cover municipal expenses, there's certainly a need to ease the property tax pressures on homeowners. And between the mayor and the council, a reasonable program of relief should be enacted promptly - with plenty of political points for all concerned.