After several days of unusually intense lobbying by Gov. Harry Hughes, the Senate tonight reversed itself and passed by a single vote a one-cent a gallon increase in the gasoline tax.

The tax, which would be used to improve roads and bridges throughout the state, faces strong opposition in the House of Delegates, where it could die or pass in the late-session bartering ahead. But tonight, the governor was savoring what several senators said was a stunning personal victory and a tribute to his powers of persuasion after the Senate's 29-to-18 rejection of the revenue-raising measure last Thursday. Tonight the tax passed 24 to 23.

One of the converted, Sen. Arthur Dorman (D-Prince George's), said his turnaround had come after his fourth meeting with Hughes, who he said had been cruelly "embarrassed" by last week's vote. "He's a Democratic governor. He shouldn't be embarrassed like that," Dorman said.

Democratic Prince George's Sen. Thomas V. (Mike) Miller expressed similar partisan concerns, announcing that he, too, had met with Hughes and was changing his vote "with my head held high."

Floor leaders fighting for the tax had delayed the reconsideration vote to give the governor time to win converts, and the final outcome was high drama mixed with political intrigue.

The vote had been scheduled for 4 p.m., but that time came and went as senators rambled on for 45 minutes over a proposed increase in the tax paid by persons who hunt deer with bows and arrows. "Anytime you have bows and arrows and muzzle loaders, it's bound to be controversial," said Sen. Harry McGuirk (D-Baltimore City) whose committee had approved the bill.

But others ascribed the prolonged debate on the measure to a strategy by gas tax proponents waiting for the arrival of Prince George's Sen. Tommie Broadwater, who had been out campaigning for Steny Hoyer in today's special primary election to fill the 5th District congressional seat of Gladys N. Spellman.

Broadwater stayed long enough to vote, and long enough to take on in debate Sen. James Simpson (D-Southern Maryland), a gas tax opponent who contended rural regions would reap too little from the new revenue, estimated at $20 million the first year. "Money is money and you've gotten a fortune out of the state," Broadwater said.

Both sides of the gas tax debate publicly praised Hughes, who has often been criticized as to passive an executive for his lobbying efforts. "I congratulate the governor," said Simpson, "because it's necessary for the governor to show strength if it's needed."

Hughes, by all accounts, did not twist arms. Instead, he reasoned and educated and, in some cases, implored. He spent 15 minutes with four Prince George's senators yesterday and converted three of them, noting his support last year for Metro subway funding. "It was just about a one-way conversation," said Sen. B.W. Mike Donovan, a vote switcher.

Ultimately, he won over Sen. John Carroll Byrne (D-Baltimore City) by providing data the legislator requested that appeared to bolster the governor's case. "I made no commitment, and he didn't ask for it," said Byrne, undecided minutes before the vote.

Hughes had previously sought a two-cent levy on top of the present 9-cent gasoline tax to replenish the depleted transportation trust fund. In an effort to win support from rural senators, Hughes and Sen. Laurence Levitan (D-Montgomery), the bill's sponsor, also accepted a rider to require state mass transit systems to collect half of their operating expenses from fares.

The bill also earmarks the funds for two years to roads and bridges and permits additional tax increases of up to four cents a gallon through 1985 depending on inflation.

"We're very pleased," said Gene Oishi, Hughes' press aide, after tonight's vote, "but it's somewhat premature to celebrate because it still has to pass the House."

A harbinger of what may be ahead appeared at the Senate door moments after the vote in the form of Del. Paul E. Weisengoff (D-Baltimore City). "Right now, it won't get two votes in committee," the legendary power broker said, "but if it passes, Hughes is going to have to change the whole state" in return.