Vice President Joe Biden has become the public face of the administration's handling of Ukraine, working to reassure Kiev and trying to talk tough with Russia.

During a whirlwind two-day visit to Ukraine, Biden met with the country's leaders and announced an additional $50 million in aid. At a press conference, he delivered a lecture to Russian President Vladimir Putin, telling him to “stop talking and start acting” to defuse the crisis.

With no diplomatic end in sight, it's a high-stakes role for a vice president whose foreign policy chops were publicly mocked by former Defense Secretary Robert Gates, who wrote in a memoir published in January that Biden was “wrong on nearly every major foreign policy and national security issue over the past four decades.”

Any missteps or another Russian land grab could prove fatal to Biden's political ambitions as he weighs a 2016 presidential bid. Critics say it will be hard for the vice president, a former chairman of the Senate Foreign Relations Committee, to separate himself from the administration's policy on Ukraine.

After his trip, late-night comics took aim at the vice president’s tendency to run at the mouth and make gaffes, joking that Putin — and everyone else — had long stopped listening to Biden.

Republican lawmakers were also unimpressed by his calls for the Kremlin to stop backing Russian separatists.

“Or else what?” asked Sen. John McCain, painting the vice president as the front man for an administration unwilling to take tough action against Russia.

Indeed, after Biden left Ukraine, it seemed that nothing had changed. Tensions with Moscow remain high, and Russian militants show no signs of backing down in eastern Ukraine.

But Biden's raising of the American flag in Kiev wasn't without benefit for President Obama, who was able to carry on with a week-long trip to Asia. And Biden's public diplomacy revealed Obama's new trust in his No. 2.

“So Biden talks a lot -- so what?” said James Goldgeier, dean of American University's School of International Service and a veteran of the Clinton White House's national security team. “The vice president has been extremely valuable to Obama --he's done everything the president could have asked for and more.”

The relationship between Obama and Biden is on the upswing following their 2012 low when the undisciplined -- but authentic -- vice president publicly supported gay marriage before the White House was ready to make the leap. Biden so angered the president's team that they reportedly froze him out of key meetings.

Since then, Obama has often turned to Biden to help in foreign policy binds — even if the assist only involves dispatching him to hot spots to repeat the administration’s line.

Despite giving his vice president a chance to raise his foreign policy credentials, Obama has stayed neutral about Biden’s political future.

“He has been, as I said earlier, a great partner in everything that I do,” Obama said, as he sat next to Biden in an interview.

“I suspect that there may be other potential candidates for 2016 who have been great friends and allies,” he added -- an awkward reference to former Secretary of State Hillary Clinton, who vastly outpolls other Democrats and whose presumed candidacy has frozen Biden in place.

At the same time, Clinton has political vulnerabilities. Her own foreign policy record is under scrutiny, especially now that her much-touted “reset” with Russia is in tatters. Clinton's “what difference does it make” remark during the Benghazi hearings cemented Republican views that the administration mishandled the terror attack that killed four Americans.

Still, Obama's relationship with Biden appears to be on the mend, possibly out of sheer necessity or long-term loyalty. The president has shown a new warmth in their relationship, posing for a selfie with Biden and joking that the two were on a “guys' trip” when they visited Pennsylvania.

Biden for his part has expressed comfort with acting publicly on Obama’s behalf even as the president’s poll numbers droop and his policies face tough criticism.

“There is nothing I would do differently,” Biden said about carrying out his job as he weighs future plans.

Many insiders believe Biden is keeping his name in the presidential mix because it's better to keep people guessing than declare the end of his long career while still in office. But Biden has made it clear he’ll enjoy the ride while it lasts.