(CNN) It's been a while since we heard much of anything from Barack Obama -- aka the 44th President of the United States.

"How did the most ubiquitous man in America for eight years virtually disappear? Over the course of his presidency, Obama cast himself as the country's secular minister as much as its commander-in-chief, someone who understood the moral core of the nation and felt compelled to insist that we live up to it. What explains his near absence from the political stage, where he might argue publicly against the reversals of his policy accomplishments, and also from American life more broadly? What is keeping him from speaking more frequently about the need to protect democratic norms and the rule of law, to be decent people? Where is the man who cried after Sandy Hook and sang in Charleston, who after each mass shooting tried to soothe an outraged nation, who spoke of American values in his travels across the globe? And, tactically, what is behind the relative silence of one of the most popular figures alive just as American politics appears to so many to be on the brink of breaking?"

Obama's self-imposed exile has been felt even more acutely by Democrats of late, as President Donald Trump has seen events conspire to hand him a golden opportunity to remake the Supreme Court and the party Obama once led has shown signs of devolving into the same sort of establishment vs. grassroots war that Republicans weathered in 2016 -- and ultimately produced Trump's candidacy and presidency.

The vacuum created by Obama's absence has led to a reemergence -- and not in a good way -- of former president Bill Clinton, who has repeatedly shown himself to be a politician well past his prim e. So, too, Hillary Clinton who seems happy to spend her time re-litigating the 2016 election

And then, on Thursday, Obama came back -- at least for a night, and reminded Democrats of what they'd been missing.

Speaking at a Democratic National Committee fundraiser in Los Angeles, Obama delivered the stop-feeling-sorry-for-yourselves speech that only he could.

"If what you are doing requires no sacrifice at all, then you can do more," Obama said. "If you are one of these folks who is watching cable news at your cocktail parties with your friends and you are saying 'civilization is collapsing' and you are nervous and worried, but that is not where you are putting all your time, energy and money, then either you don't actually think civilization is collapsing ... or you are not pushing yourself hard enough and I would push harder."

That "tough love" message is one only someone in Obama's very unique position can deliver. None of the dozens -- and I mean dozens -- of 2020 Democratic aspirants would scold the party to stop feeling sorry for itself, to stop just getting angry at Trump and to get off their asses and do something. They'd be too afraid of alienating some or all of the party base by urging them to do more. And aside from Obama, there's simply no one from the party's past -- see above on the Clintons -- who can deliver that message either.

Obama left office riding high. In a January 2017 CNN poll , 60% approved of the job he was doing -- including 95% of Democrats. No Democratic politician -- or Republican one -- has numbers like that.

What Obama's appearance Thursday night should remind everyone -- Democrats and Republicans -- is that the former president is a remarkable campaigner/candidate. His gifts on that front cannot be questioned, no matter how you assess his eight years as president. There's a reason he won with 365 electoral votes in 2008 and 332 electoral votes in 2012.

From his speaking style to his charisma, he is the best that Democrats (still) have. The question for Democrats is how much Obama is willing to do for them between now and November, particularly given his reticence to speak out against Trump to date (Worth noting: In his speech at the DNC fundraiser on Thursday night, Obama never mentioned Trump by name).

"A host of Democrats said that the former president has signaled to top lawmakers and operatives that he will be stepping up his involvement in the midterms soon and is telling friends and advisers that his priorities are flipping the House and backing up redistricting efforts led by former Attorney General Eric Holder's National Democratic Redistricting Committee.

"Obama's midterm strategy is not yet fully formed and his top advisers are still plotting the role he hopes to play the election. And while his message is a work in progress, Obama will likely urge Democrats to keep up the momentum they have shown over the last 18 months."

If Obama makes good on that plan, that's good news for Democrats. As Obama proved again Thursday night, he's the best thing the party has going for it. Still.