BERLIN (AP) — Just a few months ago, German Chancellor Angela Merkel brought together the leaders of the U.S., Britain, France and Italy to discuss the world's crises, a moment captured in a photo of the five seated around a conference table. When she hosts a summit of 20 leading global powers in July, she will be the only one of them left — and many of the policies her partners worked for might be reversed.

Merkel, the last of President Barack Obama's key European allies still standing, appears well on course to extend her 11-year grip on power, though even she warned her conservative party Tuesday that she faces her most difficult campaign yet.

Many people "feel that the world is in disarray, and they're right," Merkel told a congress of her Christian Democratic Union in Essen. "2016 hasn't made the world stronger and more stable, but rather weaker and more unstable."

"No one, even with the greatest experience, can make things better in Germany, Europe and the world more or less alone — and certainly not a chancellor of Germany," she said. "Let us not be fooled into thinking that. That would be grotesque, absurd, condemned to failure. That's not how it works."

Tamping down expectations has served Merkel well in three terms of pragmatic and rarely flashy leadership. But given the exodus of like-minded leaders, she will struggle to avoid such hopes.

In April, Merkel welcomed Obama to Germany for a meeting at which the merits of a proposed European Union-U.S. trade pact were a prominent issue. They then met British Prime Minister David Cameron, French President Francois Hollande and Italian Premier Matteo Renzi.

But at July's Group of 20 summit in Hamburg, Merkel will be facing new leaders of the West's leading powers.

Obama, whose popularity has been rising in the U.S. in recent months, tried to use his stronger standing to ensure allies on both sides of the Atlantic were in office after he leaves in January. He was mostly unsuccessful.

Obama campaigned vigorously for former Secretary of State Hillary Clinton, casting her election as a safeguard on his agenda. She lost to Republican Donald Trump, who opposes the kind of multilateral trade deals Obama tried to pursue with Europe and has called for closer relations with Russia.

Cameron was replaced by Theresa May after failing to persuade British voters to stay in the EU in a June referendum. The deeply unpopular Hollande has decided not to seek re-election in April; both of the two top contenders to succeed him advocate a softer line on Russia, and one supports leaving the EU.

Renzi announced his resignation after losing a weekend referendum on constitutional reform in Italy, leaving unclear who will take on the task of steering the country's large but troubled economy.

Obama traveled to London in April to try to boost Cameron ahead of the Brexit vote. The president bluntly warned that Britain would find itself at the "back of the queue" in trans-Atlantic trade deals if it left the EU.

This fall, Obama threw his support behind Renzi, hosting him at the White House for a celebrity-filled state dinner. He praised Renzi's efforts to modernize Italy's political institutions, calling reform an important step toward a "more vibrant, dynamic economy."

The White House has dismissed questions about whether the referendums and Trump's victory signal a broad rejection of Obama's world views, though officials privately worry about the spread of isolationist tendencies.

"I would warn against painting with an overly broad brush about the potential consequences of this outcome," Obama spokesman Josh Earnest said after the Italian vote. "There certainly is a not entirely unreasonable tendency to want to loop together the outcome in the U.K. and even the outcome of the U.S. presidential election with this outcome. But each of these is different."

Obama made no attempt to assist Hollande, and Merkel is now the last of the president's core European partners standing.

Obama has again tried to do his part to give her a boost, traveling to Germany last month to heap praise on his long-time partner.

"I value Angela's leadership," he said. "If I were German and I had a vote, I might support her."

He added: "But I don't know whether that hurts or helps."

Merkel acknowledges that she faces a tougher task this time after cruising to victory in 2013. While her conservative party is well ahead in polls, it faces new competition from the upstart nationalist Alternative for Germany party, which has thrived by attacking Merkel's migrant policies.

It also faces the possibility of three left-leaning parties linking up to put it out of government, if they can win enough votes and overcome deep policy divisions — although that currently looks like a long shot. And it must smooth over tensions with its Bavarian ally, the Christian Social Union, which has differed with Merkel over migrants.

Merkel's party re-elected her unopposed as chairwoman on Tuesday, with 89.5 percent of delegates supporting her. That was solid, but down from 96.7 percent in less-troubled times two years ago.

"The 2017 election will be more difficult than any election before, at least since German reunification," Merkel said, citing the "strong polarization of our society."

Associated Press writer Julie Pace in Washington contributed.