Washington (CNN) One hundred days before he leaves the Oval Office, President Barack Obama is showing few signs of fading into the White House woodwork.

Even as he aggressively works to elect Hillary Clinton as his replacement, Obama is also ticking off a lengthy and expanding to-do list, containing longstanding entries like closing the Guantanamo Bay prison and finally sealing a trade deal with Asia, and new vexing problems like punishing Russia for its political meddling.

His approval rating near record highs, Obama enters his final months in office with more political capital than at nearly any point in his presidency, but few obvious opportunities to expend it on the issues he hopes will form his legacy.

Obama hugs Hillary Clinton after speaking at the Democratic National Convention in July 2016. Obama told the crowd at Philadelphia's Wells Fargo Center that Clinton is ready to be commander in chief. "For four years, I had a front-row seat to her intelligence, her judgment and her discipline," he said, referring to Clinton's stint as secretary of state.

Obama hugs Hillary Clinton after speaking at the Democratic National Convention in July 2016. Obama told the crowd at Philadelphia's Wells Fargo Center that Clinton is ready to be commander in chief. "For four years, I had a front-row seat to her intelligence, her judgment and her discipline," he said, referring to Clinton's stint as secretary of state.

Cuban President Raul Castro tries to lift up Obama's arm at the end of a joint news conference in Havana, Cuba, in March 2016. Castro hailed Obama's opposition to a long-standing economic "blockade," but said it would need to end before ties between the two countries are fully normalized.

Cuban President Raul Castro tries to lift up Obama's arm at the end of a joint news conference in Havana, Cuba, in March 2016. Castro hailed Obama's opposition to a long-standing economic "blockade," but said it would need to end before ties between the two countries are fully normalized.

From left, House Majority Leader Kevin McCarthy, House Minority Leader Nancy Pelosi and House Speaker John Boehner listen as Obama speaks during a meeting in the Cabinet Room of the White House on January 13, 2015.

From left, House Majority Leader Kevin McCarthy, House Minority Leader Nancy Pelosi and House Speaker John Boehner listen as Obama speaks during a meeting in the Cabinet Room of the White House on January 13, 2015.

Obama walks to the Oval Office on August 7, 2014, the same day he announced the beginning of airstrikes on ISIS.

Obama walks to the Oval Office on August 7, 2014, the same day he announced the beginning of airstrikes on ISIS.

Actor and comedian Zach Galifianakis interviews Obama during his appearance on "Between Two Ferns," a digital video series with a laser focus on reaching people aged 18 to 34. The President urged young people to sign up for his new health care plan in the video posted on the website Funny or Die.

Actor and comedian Zach Galifianakis interviews Obama during his appearance on "Between Two Ferns," a digital video series with a laser focus on reaching people aged 18 to 34. The President urged young people to sign up for his new health care plan in the video posted on the website Funny or Die.

White House press secretary Jay Carney fields questions from reporters during a daily press briefing at the White House in September 2013. Obama had just pushed for congressional approval for limited military strikes against the Syrian government.

White House press secretary Jay Carney fields questions from reporters during a daily press briefing at the White House in September 2013. Obama had just pushed for congressional approval for limited military strikes against the Syrian government.

Hundreds of thousands gather at the U.S. Capitol building as Obama is inaugurated for his second term on January 21, 2013.

Hundreds of thousands gather at the U.S. Capitol building as Obama is inaugurated for his second term on January 21, 2013.

Obama pauses during his speech at a memorial service for the victims of the Sandy Hook Elementary School massacre in December 2012.

Obama pauses during his speech at a memorial service for the victims of the Sandy Hook Elementary School massacre in December 2012.

Obama casts a shadow in this picture as he accepts the 2012 Democratic nomination for President during the final day of the Democratic National Convention in September 2012.

Obama casts a shadow in this picture as he accepts the 2012 Democratic nomination for President during the final day of the Democratic National Convention in September 2012.

Obama sits in his chair during a Cabinet meeting in July 2012. This image was tweeted by his official Twitter account in August 2012 in response to Clint Eastwood's "empty chair" speech at the Republican National Convention. The tweet simply said, "This seat's taken."

British Prime Minister David Cameron, Obama, German Chancellor Angela Merkel and others watch the overtime shootout of the Champions League final between Chelsea and Bayern Munich in a conference room at Camp David, Maryland, during a G-8 Summit in May 2012.

British Prime Minister David Cameron, Obama, German Chancellor Angela Merkel and others watch the overtime shootout of the Champions League final between Chelsea and Bayern Munich in a conference room at Camp David, Maryland, during a G-8 Summit in May 2012.

Obama pays for a dog toy as he shops with his dog Bo at a PetSmart in Alexandria, Virginia, in December 2011.

Obama pays for a dog toy as he shops with his dog Bo at a PetSmart in Alexandria, Virginia, in December 2011.

Obama delivers remarks to troops and military families at Fort Bragg, North Carolina, on December 14, 2011, marking the exit of U.S. soldiers from Iraq.

Obama delivers remarks to troops and military families at Fort Bragg, North Carolina, on December 14, 2011, marking the exit of U.S. soldiers from Iraq.

Obama and Missouri Gov. Jay Nixon walk together in May 2011 during a tour of the tornado devastation in Joplin, Missouri.

Obama and Missouri Gov. Jay Nixon walk together in May 2011 during a tour of the tornado devastation in Joplin, Missouri.

Obama and the first lady meet with Britain's Prince William and Catherine, Duchess of Cambridge, at Buckingham Palace in May 2011.

Obama and the first lady meet with Britain's Prince William and Catherine, Duchess of Cambridge, at Buckingham Palace in May 2011.

U.S. Marines watch from Afghanistan as Obama announces the death of bin Laden on May 2, 2011.

U.S. Marines watch from Afghanistan as Obama announces the death of bin Laden on May 2, 2011.

Obama, Biden, Secretary of State Hillary Clinton and members of the national security team receive live updates on the mission to capture or kill Osama bin Laden on May 1, 2011.

Obama, Biden, Secretary of State Hillary Clinton and members of the national security team receive live updates on the mission to capture or kill Osama bin Laden on May 1, 2011.

Obama laughs as he makes a statement on his birth certificate in April 2011. Obama said he was amused over conspiracy theories about his birthplace, and he said the media's obsession with the "sideshow" issue was a distraction in a "serious time."

Obama laughs as he makes a statement on his birth certificate in April 2011. Obama said he was amused over conspiracy theories about his birthplace, and he said the media's obsession with the "sideshow" issue was a distraction in a "serious time."

Obama and his daughter Sasha swim in Panama City Beach, Florida, in August 2010, to encourage people to come back to the Gulf Coast after a devastating oil spill.

Obama and his daughter Sasha swim in Panama City Beach, Florida, in August 2010, to encourage people to come back to the Gulf Coast after a devastating oil spill.

Obama throws out the opening pitch before a baseball game between the Philadelphia Phillies and the Washington Nationals in April 2010.

Obama throws out the opening pitch before a baseball game between the Philadelphia Phillies and the Washington Nationals in April 2010.

Obama's signature on the Affordable Care Act is seen at the White House in March 2010.

Obama's signature on the Affordable Care Act is seen at the White House in March 2010.

First daughters Sasha and Malia Obama play in the snow with their father after a snowstorm hit Washington in February 2010.

First daughters Sasha and Malia Obama play in the snow with their father after a snowstorm hit Washington in February 2010.

Obama and former Presidents Clinton and George W. Bush walk to the White House Rose Garden to speak about relief efforts for earthquake-stricken Haiti in January 2010.

Obama and former Presidents Clinton and George W. Bush walk to the White House Rose Garden to speak about relief efforts for earthquake-stricken Haiti in January 2010.

Obama salutes during the transfer of Sgt. Dale R. Griffin at Dover Air Force Base in Dover, Delaware, in October 2009. Obama traveled to the base to meet the plane carrying the bodies of 18 U.S. personnel killed in Afghanistan.

Obama salutes during the transfer of Sgt. Dale R. Griffin at Dover Air Force Base in Dover, Delaware, in October 2009. Obama traveled to the base to meet the plane carrying the bodies of 18 U.S. personnel killed in Afghanistan.

Police Sgt. James Crowley, second right, of Cambridge, Massachusetts, speaks with Harvard Professor Henry Louis Gates Jr., second left, alongside Obama and Biden as they share beers on the South Lawn of the White House in July 2009. The so-called Beer Summit was held after Crowley arrested Gates at his own home, which sparked tensions and racial furor.

Police Sgt. James Crowley, second right, of Cambridge, Massachusetts, speaks with Harvard Professor Henry Louis Gates Jr., second left, alongside Obama and Biden as they share beers on the South Lawn of the White House in July 2009. The so-called Beer Summit was held after Crowley arrested Gates at his own home, which sparked tensions and racial furor.

Obama hosts the Apollo 11 astronauts -- from left, Edwin "Buzz" Aldrin, Michael Collins and Neil Armstrong -- in the Oval Office on July 20, 2009. It was the 40th anniversary of the moon landing.

Obama hosts the Apollo 11 astronauts -- from left, Edwin "Buzz" Aldrin, Michael Collins and Neil Armstrong -- in the Oval Office on July 20, 2009. It was the 40th anniversary of the moon landing.

Palestinian security forces in Jenin, West Bank, listen to Obama speak from Cairo University in Egypt in June 2009. The Palestinian Authority hailed as a "good beginning" Obama's speech to the Muslim world in which he reiterated his support for a Palestinian state.

Palestinian security forces in Jenin, West Bank, listen to Obama speak from Cairo University in Egypt in June 2009. The Palestinian Authority hailed as a "good beginning" Obama's speech to the Muslim world in which he reiterated his support for a Palestinian state.

Obama kisses Sonia Sotomayor's cheek after announcing her as his nominee for Supreme Court justice in May 2009.

Obama kisses Sonia Sotomayor's cheek after announcing her as his nominee for Supreme Court justice in May 2009.

Obama bends over so the son of a White House staff member can pat his head during a visit to the Oval Office in May 2009. The boy wanted to know if Obama's hair felt like his.

Obama and Vice President Joe Biden look at solar panels as they tour the solar array at the Denver Museum of Nature and Science on February 17, 2009. That same day, Obama signed the American Recovery and Reinvestment Act.

Obama and Vice President Joe Biden look at solar panels as they tour the solar array at the Denver Museum of Nature and Science on February 17, 2009. That same day, Obama signed the American Recovery and Reinvestment Act.

As retired military officers stand behind him, Obama signs an executive order to close down the detention center at Guantanamo Bay, Cuba, in January 2009.

As retired military officers stand behind him, Obama signs an executive order to close down the detention center at Guantanamo Bay, Cuba, in January 2009.

Obama is sworn in by Chief Justice John Roberts as the 44th President of the United States on January 20, 2009.

Obama is sworn in by Chief Justice John Roberts as the 44th President of the United States on January 20, 2009.

Obama poses in the Oval Office with several former U.S. Presidents in January 2009. From left are George H. W. Bush, Obama, George W. Bush, Bill Clinton and Jimmy Carter.

Obama poses in the Oval Office with several former U.S. Presidents in January 2009. From left are George H. W. Bush, Obama, George W. Bush, Bill Clinton and Jimmy Carter.

Obama stands on stage in Chicago with his family after winning the presidential election on November 4, 2008.

Obama stands on stage in Chicago with his family after winning the presidential election on November 4, 2008.

First lady Michelle Obama brushes specks from the coat of then-Sen. Obama in Springfield, Illinois, just before he announced his candidacy for President in February 2007. Their daughters Malia, left, and Sasha wait in the foreground.

First lady Michelle Obama brushes specks from the coat of then-Sen. Obama in Springfield, Illinois, just before he announced his candidacy for President in February 2007. Their daughters Malia, left, and Sasha wait in the foreground.

U.S. President Barack Obama attends the Nuclear Security Summit in the Hague, Netherlands, in March 2014. As Obama's second term nears its close, here's a look at some key moments of his administration.

U.S. President Barack Obama attends the Nuclear Security Summit in the Hague, Netherlands, in March 2014. As Obama's second term nears its close, here's a look at some key moments of his administration.

Congress has shown little appetite to advance his agenda, even in the lame duck period between November's vote and Inauguration Day in January. Even on issues where most Republicans agree with Obama -- namely, the Trans-Pacific Partnership (TPP) trade deal -- GOP congressional leaders have downplayed the potential for action.

On many issues, Obama will be faced with a choice between deploying his executive powers -- a tactic he's used frequently -- or leaving some of his unfinished business for his successor.

Overseas, Obama confronts knotty diplomatic and military quandaries that he hopes to straighten out for the next commander in chief. But there's little doubt the global flash-points that he's struggled to contain will persist well past next year.

"I think the President is approaching the final 100 days the way that approached the previous seven-and-a-half years or so, which is seeking to make the most of every remaining opportunity," said White House spokesman Josh Earnest on Wednesday. He said he doubted Obama was even aware he was crossing the 100-day mark.

Lame-duck dilemmas

Obama hopes to capitalize on the lame-duck session of Congress to complete at least one major outstanding issue: his stalled nomination of Merrick Garland to the Supreme Court. Republicans, who have resisted bringing Garland up for a vote over the past year, could conclude the moderate appeals court judge is more acceptable than whatever nominee Hillary Clinton or Donald Trump puts forward should they win.

Clinton hasn't said definitively whether she would reappoint Garland or select her own nominee, leaving the confirmation process post-Election Day unclear. Republicans, who have insisted the next president should pick the ninth justice, risk political backlash if they decide to embrace Garland in the lame duck. The same is true for another controversial nomination pending: Obama's pick to be the first US ambassador to Cuba in more than 50 years.

President Barack Obama nominates Judge Merrick B. Garland to the US Supreme Court, in the Rose Garden at the White House on March 16, 2016.

And it's true as well for TPP, which both Clinton and Trump have said they'll reject if elected. With Congress avoiding a vote on the plan before Election Day, Obama has remained optimistic for action once lawmakers learn their fates in November.

"After the election, I think people can refocus attention on why this is so important," Obama said in Asia during a trip in September.

White House officials also say movement on criminal justice reform -- long the priority of a ideologically diverse group of unlikely allies -- is likely during the lame duck. Proposals include altering harsh sentencing laws and returning some rights, including voting rights, to convicted felons.

"It's a remarkable coalition of groups both on the left and on the right that have really come together to push this for a variety of different reasons," said White House counsel Neil Eggleston in an interview last week. "We continue to think and are working hard to get it done in the lame duck."

Eggleston said the spate of commutations for non-violent drug offenders will continue apace as Obama works around Congress to instill fairness into the system. Presidents typically scale up their use of pardon and clemency powers in the final months of their administrations.

Obama also faces perhaps his most disappointing unfulfilled promise as he wraps his term: the prison at Guantanamo Bay, whose population has been winnowed to 61 from the hundreds who were detained there at the beginning of Obama's presidency. A White House plan to transfer some prisoners into American prisons was rebuffed by lawmakers, who would need to alter current law to allow transfers onto US soil.

At the White House Wednesday, Obama acknowledged at least some of his remaining tasks would likely become jobs for his successor.

"We've done a lot of work together, but we know we've got more work to do," Obama said during a reception for Hispanic Heritage Month. "We've known all along that we weren't going to get everything done during one presidency."

Looking for blank slates

A daunting range of national security challenges still confront Obama as he enters the final chapter of his presidency. Responding to the latest -- a US intelligence determination that Russia is likely trying to meddle in the presidential contest through hacking -- will add to Obama's punch list in his final stretch in office.

The US is mustering a "proportional response," the White House said this week, without specifying specifically what's in store for Moscow. Likely options include financial sanctions or legal action through the Justice Department. But even after Obama makes his move, Russia's provocations aren't likely to cease.

Obama still hopes to reach an agreement with Russian President Vladimir Putin to end suffering in Syria, where the Russians have sided with Bashar al-Assad to crack down on opposition fighters. He has little time to find a solution before Aleppo, Syria's besieged second city that's under partial rebel control, falls completely to the regime.

In Iraq, Obama is preparing for an offensive to liberate Mosul from ISIS by sending 600 more US troops to help train Iraqi forces. It's a mission that's not likely to be complete by the time Obama leaves office on January 20.

And administration officials are still holding out the chance Obama could offer a parting stab at brokering peace between Israel and the Palestinians, either by laying out a framework for talks or supporting a UN Security Council resolution spelling out details of an agreement.

Obama is due to travel abroad once more as president, to Peru for a meeting of Asia Pacific leaders. It's likely additional countries are added to his November itinerary to form a farewell tour. Obama could always choose to make a final secret visit to Iraq or Afghanistan as well.