Were Lieutenant Governor David Paterson to assume the governorship, he could find himself quarantined within New York State to avoid ceding power temporarily to Governor Spitzer’s arch-rival, the Republican state Senate majority leader, Joseph Bruno.

Because of a quirk in the state’s constitution, which does not outline a process for replacing a lieutenant governor who becomes governor, executive power would be granted to the Senate majority leader if the acting governor crossed the state line or became incapacitated.

“Essentially he would have the powers of the governor,” the deputy director of the Rockefeller Institute, Robert Ward, said of Mr. Bruno’s status should Mr. Paterson leave town. His powers would include issuing executive orders, hiring and firing staff, approving expenditures that have been appropriated but not yet spent, issuing pardons, and calling in the National Guard, among others. Mr. Bruno could even sign legislation the governor had planned to veto, were it to reach his desk.

“He could try to appoint judges and have them confirmed by the Senate,” a former parks commissioner and director of New York Civic, Henry Stern, said of Mr. Bruno. “Paterson should definitely not visit Australia or New Zealand, let’s put it that way.”

While most of these moves would be reversible, some — such as a judicial appointment or the spending of state funds — would not.

According to Mr. Ward, a Paterson administration would have at least one potent weapon to impede a rogue acting governor: bureaucracy. The governor’s appointees could slow their offices’ operations to a crawl in order to allow him time to race back and regain control of the state. But if Mr. Paterson were incapacitated for a stretch of time, as happened to Governor Corzine of New Jersey after a life-threatening car accident, Mr. Bruno could get comfortable as the state’s leading official.

Mr. Ward said an incapacitated governor could serve as a flashpoint for legal battles “If such a thing were to go on for awhile, you could almost bet there would be lawsuits of some kind or another,” he said.

A state executive office divided by party is not unprecedented in New York. In 1985, Governor Cuomo’s first lieutenant governor, Alfred Del-Bello, quit his post, leaving the Republican Senate majority leader, Warren Anderson, to temporarily fill his role. “The question did arise then as to whether anything would change when Governor Cuomo was out of state, and no doubt it will arise again,” Mr. Ward said.

Mr. Anderson’s period as second in command passed without incident, and Mr. Cuomo won reelection in 1986 with a new lieutenant governor.

This time around, Mr. Ward said he thought Mr. Bruno was unlikely to attempt any kind of quasi-coup. One factor that might prove helpful in keeping the peace is that the two lawmakers are said to be on friendly terms. Colleagues of Mr. Paterson say he was often willing to work with Mr. Bruno and other Republican lawmakers during his time as Senate minority leader.

“In general, they have a respectful relationship,” Assemblyman Dov Hikind, who represents parts of Brooklyn, said of the two officials yesterday. “That’s the way David is, he just gets along with people who are the same and who are different.”

Senator Bill Perkins, who represents parts of Manhattan, said yesterday that a power struggle was unlikely. “I can’t even imagine that scenario right now,” he said in an interview. “I think everyone right now is just trying to get the ship ashore and guide it through these rocky waters.”

Relationships can sour, though, and the executive power issue could come to the forefront should Messrs. Bruno and Paterson find themselves in an acrimonious political struggle similar to what Mr. Spitzer has endured with the majority leader.

“When people are at each other’s necks it’s another story, but I think if David Paterson becomes governor there will be a whole different atmosphere,” Mr. Hikind said yesterday. “Otherwise, jets are pretty fast and you can get back if you want.”