The six state senators from Montgomery County and the Senate president sent a veiled threat to Gov. Harry Hughes today, adding to the obstacles in the way of the proposal to raise the state's tax on gasoline.

The senators, who form a pivotal voting bloc for the already imperiled proposal, asked Hughes to work out a new formula for distributing gasoline tax revenue to the state's 23 counties and Baltimore. Hughes has asked for a 4 percent tax on the wholesale price of gasoline in addition to the existing 9-cent per gallon tax at the pump; legislative leaders are trying to come up with a compromise that would result in a smaller tax increase.

The senators did not say they would block a tax increase unless Montgomery gets a larger share of revenue. But they came close to that in their letter to the governor, which said, "we are hesitant to approve a tax increase that may prove inequitable."

"If Harry wants us to go to the wall on a tax increase in an election year, he's got to give us some quid pro quo," said Sen. Victor L. Crawford, chairman of the Montgomery County Senate delegation.

That delegation and Senate President James Clark Jr. (D-Howard /Montgomery) think the current formula is weighted too heavily toward Baltimore. Under that formula, Baltimore receives more than any other locality.

The Montgomery delegation says the current arrangement is a holdover from the days when Baltimore controlled the state politically, not taking into account the city's decreasing population and political clout, or the ascendancy of Montgomery as the state's wealthiest county and one that has increasing political power.

The Montgomery County senators hope their united front will force Baltimore to the negotiating table. But Baltimore lawmakers seemed in no hurry today to negotiate away a formula that has benefited the city for more than three decades, and the possibility is raised of a stalemate that could threaten the entire tax.