A divided Maryland Senate revived one of the most entertaining battles of the 1985 session yesterday when it approved, on a vote of 28 to 19, a measure to reverse a 20-year-old ban on slot machine gambling. The bill would allow charities on the Eastern Shore to own and operate the devices.

The measure, which now goes to the House of Delegates, is similar to a bill enacted last year after an intense behind-the-scenes lobbying effort.

That legislation was vetoed by Gov. Harry Hughes.

This year's bill applies to eight of the nine Eastern Shore counties, excluding Worcester, home of the resort community of Ocean City.

It allows nonprofit fraternal and charitable organizations to operate up to five slot machines each on condition that at least half of the money go to charity.

The measure was prompted by a state police raid last year on two dozen Eastern Shore clubs where slot machines were being operated.

Though scores of machines and several thousand dollars were confiscated, prosecutors questioned whether state law was actually violated.

No prosecutions resulted from the raids.

Supporters pushed the measure to clarify whether the clubs could operate the machines, but opponents have argued that a return to legalized slot machine gambling could provide an opening for organized crime to gain a foothold in the state.

"It was a time when there was an inordinate concentration of power [in the holders of gaming licenses], in the hands of people who bought and sold zoning . . . and bought and sold politicians like bananas," said Sen. John A. Cade (R-Anne Arundel).

But Sen. John Coolahan (D-Baltimore County), called such concerns "hypocrisy," arguing, "What's the lottery? Gambling my friends, gambling . . . . What's horse racing in this state? That's been going on for 300 years. You don't go out there because you want to see the animals run, you go out there because you want to make a few bucks off of them."