The past year in the political career of Maryland Gov. Martin O’Malley (D) will be remembered as one in which he spread his wings far from Annapolis. The start of the coming year is shaping up as a reckoning back in the state capital.

O’Malley is gearing up to push his most ambitious — and politically perilous — 90-day legislative agenda since taking office in 2007. His success or failure in a state dominated by fellow Democrats could well determine whether talk continues about a future beyond Maryland.

When lawmakers return in January, O’Malley has pledged to spearhead the fight to make Maryland the seventh state to legalize same-sex marriage, following closely in the wake of New York.

He plans to resurrect two leading environmental priorities that the General Assembly rebuffed last session — jump-starting the state’s wind-power industry and sharply limiting the use of septic systems in new residential developments. He is likely to champion increases in the state’s gas tax and so-called flush tax, casting those moves as an effort to rebuild Maryland’s transportation and sanitation infrastructure and create jobs.

In an interview, O’Malley said that with the state facing another $1 billion shortfall in its operating budget, he may propose other tax increases as well as unpopular spending cuts to close the gap.

On top of all of that, O’Malley must introduce a redistricting plan for the General Assembly. And the governor is certain to get drawn into several other high-profile issues not of his making, such as a bid to bring slot-machine gambling to Prince George’s County.

With so many issues on his plate, few in Annapolis expect the governor to prevail on every front. O’Malley did not volunteer a yardstick for success but acknowledged that some agenda items will be difficult.

“We have a lot of big issues on the horizon, and we plan to address them,” he said.

Others suggest that if he finishes with several big wins, O’Malley has a chance to bolster his legacy in Maryland and build a case for national office. But high-profile defeats could undercut his effectiveness for the rest of his term and raise questions about whether he’s ready for bigger things.

“I don’t know how you get it all done,” said Del. Dereck E. Davis (D-Prince George’s), a leading voice in the House of Delegates. “It’s a heavy lift for one session. It may be a heavy lift for an entire term. I’ve got to tip my hat to them for their ambition.”

The governor played down any broader implications of the looming session for his future. But supporters and detractors alike see a lot at stake for O’Malley, who has served for the past year as chairman of the Democratic Governors Association, taking aim at Republicans at the state and national levels.

O’Malley, who is widely expected to get the nod next month from his fellow governors to lead the DGA for a second year, has used the perch to travel the country and appear on Sunday talk shows, fueling speculation about interest in a 2016 presidential bid.

Mike Morrill, a longtime Democratic strategist in Maryland, said that whatever O’Malley’s future holds, he will benefit if he can get things done in Annapolis at a time when Washington appears so dysfunctional. “People have begun to think on the national level that even small things can’t get through,” Morrill said.

House Minority Leader Anthony J. O’Donnell (R-Calvert) said O’Malley appears to be playing to a national audience of liberal activists key to his future ambitions.

“He might be able to force this agenda through in Annapolis, because he has a lot of tools at his disposal,” O’Donnell said, “but the citizens of Maryland are not going to look kindly at who-knows-what tax and fee increases and a very liberal social agenda.”

Even in a legislature with lopsided Democratic majorities, few of the high-profile issues O’Malley plans to push are sure things.

A possible increase in the gas tax offers a case in point. A blue-ribbon commission has recommended raising the 23.5-cents-per-gallon tax by 15 cents over three years, citing a state transportation system “on the verge of financial collapse.”

O’Malley stopped short of embracing that plan but said “we’ve got to do something.” He said he is looking at “the fairest way” to raise additional dollars to maintain Maryland’s roads, bridges, tunnels and mass transit.

“None of these, I would suggest, are slam-dunks,” House Speaker Michael E. Busch (D-Anne Arundel) said when asked about a possible gas tax increase and high-profile issues O’Malley is pushing.

O’Malley said he is also considering an increase in the state’s “flush tax,” a fee on both sewer and septic users that now amounts to $30 a year. Legislation passed in 2004 under O’Malley’s Republican predecessor earmarks the funds for upgrades of Maryland’s larger wastewater treatment plants. Forecasts by state analysts suggest that the fee needs to be more than double to generate enough money to finish the work.

“As Marylanders, we have a tradition of leading by example,” O’Malley said. “There are a lot of jobs that can be produced by repairing our infrastructure.”

In 2007, O’Malley expended a great deal of political capital pushing a broad range of tax increases, including that of the sales tax rate, to help close a $1.5 billion budget shortfall.

Since then, the governor has relied far more on spending cuts to balance a succession of recession-battered budgets. But he said he is looking at “a whole range of options, both cuts and revenues,” to close next year’s projected gap.

O’Malley also said he is likely to bring back, perhaps in amended form, two bills on which he suffered defeats last session. One sought to spur the construction of offshore wind farms by requiring the state’s utilities to enter into long-term agreements with providers of that clean-energy source.

O’Malley said he is open to considering another approach, modeled after New Jersey’s, which provides incentives for offshore wind generation but requires less of an upfront commitment from the utility companies. Maryland provides incentives for solar energy in a similar fashion.

O’Malley said an effort to limit new residential septic systems “remains very much on the agenda.” His embrace of such legislation several weeks into the last session caught lawmakers off guard and drew staunch opposition from those from rural areas.

He said he was awaiting the work of a task force before deciding how to amend his proposal.

The governor also said two priorities of the state’s gay rights lobby will have his full support: a bill expanding protections for transgender people, which failed in the Senate last session; and the same-sex marriage bill, which fell short in the House.

O’Malley, whose lobbying on the gay nuptials bill was largely limited to closed-door meetings last session, has pledged to sponsor the legislation in the coming session. His announcement in July closely followed passage of a bill in New York, championed by Gov. Andrew M. Cuomo, another Democrat whose star is rising nationally.

O’Malley said he and his aides have focused on about 15 delegates whose votes are in question.

Busch, who supports the bill, suggested that the number of delegates in play may be smaller than that, but he said he welcomes O’Malley’s efforts. “We worked very hard last session,” Busch said. “I think having the full force of the governor’s office behind it makes a big difference.”