WASHINGTON — Buoyant in political victory, President Barack Obama on Wednesday wrapped up a long, rough year in Washington by rejoicing in a rare, bipartisan "season of progress" over tax cuts, national security and civil justice. Halfway through his term, he served notice to his skeptics: "I am persistent."

The president who strode on stage for a news conference cut a remarkably different figure than the Obama who, just seven weeks ago, held a similar event in which he somberly admitted he had taken a "shellacking" in the midterm elections and needed to re-evaluate. This time, Obama was about to jet off to a Hawaiian holiday vacation knowing he had secured the kind of legislative wins that rarely come so bundled as they just did, particularly in a postelection lawmaking session.

Obama spoke on the same day that he found enough allies in both parties to get Senate ratification of a nuclear arms treaty with Russia, a vote watched around the world as a test of international security and presidential clout. He also signed landmark legislation to allow gays to serve openly in the military, calling himself overwhelmed by the enormity of the moment.

And that was on top of other achievements, including a hard-fought deal to extend tax cuts and unemployment insurance even as it piled on more debt, a broad food security bill, a trade deal with South Korea and declarations of progress in the widening war in Afghanistan.

"If there’s any lesson to draw from these past few weeks, it’s that we are not doomed to endless gridlock," Obama said. "We’ve shown in the wake of the November elections that we have the capacity not only to make progress, but to make progress together."

That spirit may be fleeting.

Obama was able to get the votes he needed in a lame-duck session in which his party still controlled the House and Senate, retiring or ousted members could act knowing they would no longer face voters, and the potential of a politically devastating tax hike on Jan. 1 forced lawmakers into action. None of those factors will be in play come January when Republicans take control of the House and have a greater voice in the Senate as well.

To a nation long tired of political gamesmanship, Obama used the moment to try to put himself above it — and to challenge both parties to join him. He said voters wanted this "season of progress," promising to stick with that mission and hoping "my Democratic and Republican friends will do the same."

He also did not get all he wanted, losing some fights and swallowing a two-year extension of tax cuts for wealthier people as part of the tax deal.

Obama underscored his agenda ahead, much of it amounting to unfinished promises: deficit reduction, energy innovation, immigration reform, the closing of the Guantanamo Bay prison, education and research investments, and the biggest item of all: finding ways to create more jobs for millions of hurting Americans.

In the course of questioning, Obama revealed that his position on gay marriage is "constantly evolving." He has opposed such marriages and supported instead civil unions for gay and lesbian couples. The president said such civil unions are his baseline — at this point, as he put it.

"This is something that we’re going to continue to debate, and I personally am going to continue to wrestle with going forward," he said.

The slow progress on the economy continues to pull down the spirits of the country and threaten to overshadow many of Obama’s other successes. Unemployment was measured at 9.8 percent in November, down only slightly from its double-digit high in 2009. Obama sought to broaden the burden of responsibility to Republicans for a faster economic rebound, saying "people are going to be paying attention to what they’re doing as well as what I’m doing."

Obama sought to give credit to Congress, and chiefly the Democrats who have been running it, for what he called the most successful post-election period in decades. But he also sought to assert his own role and power, just weeks after his relevancy had been called into question.

"One thing I hope people have seen during this lame duck: I am persistent," Obama said. "If I believe in something strongly, I stay on it."

He saved his most emotional appeal for committing anew to the DREAM Act, a measure which would offer a path to legal status for young illegal immigrants who enroll in college or join the military. It died in Congress in the waning days of the session, overwhelmed by Republican opposition. Obama said those young people live in fear of deportation.

"It is heartbreaking," he said. "That can’t be who we are."

Obama also promised that deficit reduction would be a major issue in 2011. The midterm elections were seen in part as a reflection of how many Americans are sick of Washington’s spending ways, and promises over the years to rein in deficit spending have fallen short of reality when the choices get tough.

"I guarantee you, as soon as the new Congress is sworn in, we’re going to have to have a conversation about, how do we start balancing our budget or at least getting to a point that’s sustainable when it comes to our deficit and our debt?" he said.