Washington (CNN) Former President Barack Obama used an appearance at a high-dollar donor confab on Friday to urge the field of Democratic presidential hopefuls to "pay some attention to where voters actually are," warning them about going so far on certain policies that they become out of step with voters.

Obama said that some Democrats are listening too closely to liberal Twitter and progressive activists, specifically singling out issues like health care and immigration and, in what amounted to a stern warning to the 2020 field, bluntly said that voters are "less revolutionary than ... interested in improvement" and warned about turning off certain segments of the electorate by not being "rooted in reality."

"My one cautionary note is I think it is very important for all the candidates who are running at every level to pay some attention to where voters actually are," Obama said, specifically saying he doesn't think candidates should be "diluted into thinking that the resistance to certain approaches to things is simply because voters haven't heard a bold enough proposal."

The former president specifically noted health care and immigration, saying people are "rightly ... cautious" on health care because "they don't have a lot of margin for error."

Obama's comments are particularly noteworthy because he rarely comments on the Democratic field, aside from -- as he did on Friday -- promising to "work my tail off to make sure" whoever wins the nomination defeats President Donald Trump.

Obama said his comments were not meant to be a "criticism to the activist wing" because those people should be pushing the party, but added that the "candidates' job, whoever that ends up being, is to get elected" and warned them from thinking that "if you get so far out and you think automatically people will follow" because you are being "bold and creative."

The former president's comments come at the same time that the party -- led by the large field of presidential hopefuls -- debates a host of sweeping policy proposals. These include "Medicare for All," a liberal proposal to remake the country's health care system, the Green New Deal, a sizable plan aimed at combating climate change, and policies like decriminalizing border crossings into the United States and remaking the Supreme Court.

"This is still a country that is less revolutionary than it is interested in improvement. They like seeing things improved, but the average American doesn't think you have to completely tear down the system and remake it," he said. "I think it is important for us not to lose sight of that."

Obama also used the appearance to urge members of the Democratic Party to stop worrying so much about the turmoil and tumult within the Democratic race for president.

"For those who get stressed about robust primaries, I just have to remind you that I had a very robust primary," Obama said, nodding to his 2008 race against then-Sen. Hillary Clinton, which dragged on for months.

He added: "I am confident that at the end of the process we will have a candidate who has been tested and will be able to proudly carry the Democratic banner, and we are going to have to unify around that."

The forum for the comment was not lost on those in the room: Obama offered his advice during an onstage interview with former Georgia gubernatorial candidate Stacey Abrams at an event hosted by Democracy Alliance, a club of the party's top donors, the same group of people whose private and public worrying about the 2020 race has led some Democrats who had ruled out bids to consider getting back in.

The field of Democrats vying to take on Trump has grown in recent weeks, not shrunk, with former Massachusetts Gov. Deval Patrick launching a late-entry presidential campaign on Thursday.

Patrick, who jumped into the race out of fear over the state of the current crop of Democrats, has since subtly knocked his Democratic opponents, casting the race as one between "nostalgia" -- a nod to former Vice President Biden -- and the idea that "it is our way, our big idea, or no way" -- a nod to Sens. Elizabeth Warren of Massachusetts and Bernie Sanders of Vermont.

Democratic donors, watching Biden struggle to break out in the crowded field and liberals like Warren and Sanders pick up momentum, have been whispering for weeks that other Democrats should consider shaking up the race. Their key concern: None of the current candidates could defeat Trump if the election were today, despite polls that show otherwise.

Former New York Mayor Michael Bloomberg is also publicly weighing a run , after ruling it out earlier this year, because of concerns about Biden's ability to win the primary and go on to beat Trump.

Obama said Friday that debates within the party are good for the eventual nominee, and that losing states in 2008 had made him a better president.

"If Iowa showed that I could win the presidency, New Hampshire showed I could handle the presidency," he said, "because when you are president you also experience losses and setbacks and things don't break your way."

Obama's most stinging indictment of the party came during his warnings to its field of 2020 presidential candidates.

He showed that he was closely watching the Democratic race, especially how the candidates were debating his legacy and policies he had enacted during his eight years in the White House.

"Let people hear directly from me on this: I think it is important for candidates to push past what I was able to achieve as president. I wouldn't run the same campaign today in this environment that I ran in 2008, in part because we made enough progress since 2008, of which I am very proud, that it moved what is possible," he said. "So I don't want people to just revert to what is safe. I want them to push on and try more."

He added: "So I don't take it as a criticism when people say, 'That is great, Obama did what he did and now we want to do more.' I hope so. That is the whole point. I built off the progress other people made. And tried to take the baton and run the race a little further, and then I expect people to take the baton from me and then I want them to run it a little further from that."