The D.C. statehood convention neared completion of a suffrage article in its proposed constitution last night that would leave the politically tricky task of redefining state election districts to an independent "reapportionment commission," rather than the legislature.

The five-member, multiparty commission, appointed by the governor of the new state, would redraw the legislative districts of the city after each decennial census to keep their populations roughly equal.

The reapportionment commission is a relatively new but increasingly popular mechanism. It exists in Hawaii and a few other states, replacing the more traditional process in which members of state legislatures reapportion their own districts, sometimes after bitter fighting and gerrymandering.

A special feature in the D.C. reapportionment provision is a ban against using "the addresses of incumbent legislators" as a basis for redrawing legislative boundaries--a deliberate device to avoid the type of situation that occurred in the recent redistricting of Wards 2 and 3 here in which the Georgetown home of Ward 3 City Council member Polly Shackleton was sliced out of the rest of Georgetown when it was reassigned to Ward 2.

Other elements of the suffrage article approved on first reading so far include:

* Establishment of voter qualifications. Voters would have to be at least 18 years old, residents of the city and not mentally incompetent or imprisoned for a felony.

* Referendum. Registered voters would be able to mount referendum campaigns to overturn legislation during a 90-day period after passage. A bill would not go into effect during the 90-day period nor until the referendum was held at least 60 days after the 90 days.