Former Vice President Joe Biden is dropping in the polls in the presidential race while a self-described Democratic socialist is on the rise. In the still-crowded field, he’s been losing support to other moderates.

Speaking to donors in Denver Monday night, Biden never referred to those polls or his declining position after disappointing finishes in Iowa and New Hampshire this month. But it was clear he was seeking to regain lost ground.

He took aim at U.S. Sen. Bernie Sanders, the emerging front-runner, by criticizing him for not adequately explaining how he’d pay for his Medicare for All plan. Biden has offered more modest health care proposals, including a public option insurance plan, that would cost a fraction as much.

“Folks, what the voters are looking for, in my view, is they’re looking for authenticity,” Biden said. “The last thing we need to be running against the president — this president, this charlatan, this guy who is a serial liar — is to be in a position where we’re not absolutely able to completely level with the American people (about) what things are going to cost and what it’s going to cover.”

A few moments later, Biden suggested Sanders’ plan had no chance of passing Congress: “It’s not enough to be able to beat Trump. You’ve got to be able to bring along the Senate (to a Democratic majority) and keep the House in order to get things done.”

At another point, after recounting his role in getting President Barack Obama’s Affordable Care Act passed in 2010, Biden took a dig at self-funding billionaire Mike Bloomberg, who’s been rising in the polls.

“By the way,” Biden said, “Mayor Bloomberg says the health care bill was a disaster, it’s a lousy bill. But he has $60 billion to explain that.”

Biden tried to make the case to 175 people assembled in northwest Denver that he was the surest bet to defeat President Donald Trump in November. They gathered at the home of Ken Salazar, the former U.S. senator and Interior secretary, and his wife, Hope Hernandez-Salazar.

Also on hand were several current and former elected officials, including Colorado Secretary of State Jena Griswold, Treasurer Dave Young and state Senate President Leroy Garcia.

Biden swung through Colorado to ask donors for help ahead of the state’s March 3 primary, on Super Tuesday. Unlike other leading candidates, he hasn’t held any public campaign events in Colorado.

The last time he visited the state was for a September fundraiser in Denver. At the time, Biden was leading the national polls. But he returned Monday in a weaker position, with his polling numbers dropping sharply since late January.

He’s now ranked second in Real Clear Politics’ national polling average, behind Sanders, who drew thousands of supporters to a Denver rally Sunday. In the New Hampshire primary last week, Biden placed fifth.

He’s hoping to come back in the next two weeks in Nevada and South Carolina, which have more diverse populations.

Salazar enthusiastically boosted Biden, crediting him for being “one of the creators of the health care revolution that we’re seeing, with a lot more work to do.” He noted that his older brother, John Salazar, had lost his seat in Congress in part because of his vote for the health care law.

“By the way, that was a courageous vote you took,” Biden said.

“I’d do it again!” John Salazar yelled from the back of the room.

Biden argued that despite the nation’s strong economy, under Trump, “an awful lot of middle class folks are being left behind – really left behind.”

He said he wants to “rebuild the backbone of the country, the middle class, and this time bring along all the brown and black folks all across the board.”

Biden grew particularly animated when talking about Trump’s foreign policy, raising his voice a few times.

“What he is doing to this country is absolutely appalling,” Biden said. “In the lifetime of anyone in this room, and those of our parents as well, we’ve never seen a president like this. We’ve never seen a president who’s weaponized the Justice Department, denigrated the armed forces, (treated) our allies in a way that creates distance with them, and (who) embraces thugs and autocrats from Putin to Kim Jong-Un. …

“So folks, there is a whole lot to do. But I’m optimistic.”