Sen. Bernie Sanders, after a drubbing in the latest round of primaries, vowed Wednesday to press on with his presidential campaign -- touting the appeal of his progressive message and suggesting front-runner Joe Biden has not attracted a sufficient following among young voters.

The decision from the populist senator from Vermont came the day after he was pummeled by the former vice president in Michigan, Missouri, Mississippi and Idaho and failed to have a breakout performance in Washington state. As the bad news from the six March 10 contests continued to roll in Tuesday night, the self-described democratic socialist headed home to Burlington, Vt., and took the unusual step of not giving a prime-time primary night speech.

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He emerged Wednesday afternoon to discuss his plans.

“Last night, obviously was not a good night for our campaign, from a delegate point of view,” Sanders said, speaking to reporters from Burlington.

But looking for the silver lining, he touted his victory in North Dakota and noted he's leading in the Washington state vote count. Making clear his intentions, he said he plans to see Biden at the next debate on Sunday in Phoenix.

Sanders, hinting at his decision-making process later in the calendar, stressed the importance of defeating President Trump and said he'd do "everything in my power" to make that happen.

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But he took a swipe at Biden's current coalition. "You need to win the voters who represent the future of our country and you must speak to the issues of concern to them," he said. "... You cannot simply be satisfied by winning the votes of people who are older."

Declaring he's won the "ideological debate," Sanders acknowledged his campaign is losing the debate over electability.

Sanders shared that he and his campaign have heard directly from countless voters who say they like the senator's proposals but think Biden has the better chance at defeating the president in November's general election.

"I strongly disagree with that assertion but that is what millions of Democrats and independents today believe," Sanders acknowledged.

He rejected the argument that he is not well-positioned to go up against Trump.

Looking ahead to his upcoming one-on-one showdown with Biden in prime-time, Sanders said that "on Sunday I very much look forward to the debate in Arizona with my friend Joe Biden."

And he shared some of the questions he hopes to ask his rival on the debate stage.

Among them were "what are you going to do for the 500,000 who go bankrupt in our country because of medically related debt and what are you going to do for the working people of this country and small business people who are paying on average 20 percent on their incomes for health care?"

Sanders said he'll also quiz Biden on whether the former vice president is "really going to veto a Medicare-for-all bill if it is passed in Congress."

And he pledged to ask Biden "what are you going to do to make sure that all of our people can go to college or trade school regardless of their income and what are you going to do about the millions of people who are struggling with outrageous levels of student debt."

But Sanders -- for the first time in a couple of weeks -- refrained from directly attacking Biden for his past votes greenlighting the Iraq War and favoring trade deals. The noticeable shift seemed to indicate Sanders had changed his mission from trying to defeat Biden to attempting to sway Biden to accept the proposals Sanders and his supporters have long sought.

And Sanders has plenty of clout for the mission ahead. Biden, attempting to unite the party in order to try and defeat Trump in November's general election, desperately needs Sanders and his legions of young supporters firmly on his side.

The Biden campaign - asked for a response to Sanders' speech - told Fox News "last night, Joe Biden expanded his coalition and continues to demonstrate he is the candidate who can unite the Democratic Party. Our campaign is focused on the task at hand: defeating Donald Trump so we can make real, lasting progressive change in this country and in people's lives."

Sanders was the front-runner in the Democratic nomination race last month, thanks to his virtual tie in Iowa’s caucuses, outright victory in New Hampshire’s primary, and a shellacking of Biden and the rest of the field in Nevada’s caucuses.

Biden, nearly left for dead, mounted a lighting-fast comeback, starting with his landslide victory in South Carolina at the end of February followed by sweeping victories three days later on Super Tuesday. Biden’s assembled a large coalition of voters – solidly winning among African-Americans, women, suburban and rural voters. While Sanders remained strong among younger voters, he's failed to expand upon his base, and his electability argument with white working-class voters was shattered by Biden in Michigan’s primary.

Biden’s blockbuster performance in Tuesday’s contests boosted his lead in the all-important race for presidential convention delegates and further cemented his status as the undisputed front-runner for the Democratic nomination. He also has steadily racked up endorsements from former rivals and party establishment figures, wary of entertaining the kind of damaging primary waged between Sanders and Hillary Clinton in 2016.

This presents Sanders with a difficult choice to make on how long to continue his White House bid as any realistic chance of winning the nomination dims.

The upcoming primary calendar appears to only make matters worse as his window for nomination closes.

The large states of Florida, Illinois, Ohio, and Arizona all hold primaries next Tuesday, followed a week later by Georgia. Sanders lost all five of these states in the 2016 Democratic race to eventual nominee Clinton.

At last count, Sanders had slipped more than 160 delegates behind Biden, and it’s extremely challenging for the senator to make up such ground in the upcoming contests. Recent political history looms over the current race.

Sanders, an independent lawmaker who’s represented Vermont first in the House of Representatives and currently in the Senate for three decades, was the longest of long shots when he launched a Democratic nomination bid in the 2016 cycle. After nearly defeating Clinton in Iowa and then trouncing her in New Hampshire, Sanders battled Clinton through the end of the primary calendar before endorsing her in the summer. But the tensions and friction between the two camps and their supporters persisted, and contributed to Clinton’s loss in the general election to Donald Trump.

Sanders formally launched his second presidential campaign in February of last year. After suffering a heart attack last October, some pundits started to write Sanders’ political obituary. But as fellow progressive champion Sen. Elizabeth Warren’s presidential campaign faltered in the late autumn into the early winter, Sanders’ fortunes dramatically improved as his poll numbers rose and he hauled in a massive amount of grassroots campaign cash from small-dollar contributors.

That changed starting in South Carolina.

Fox News' Andrew Craft contributed to this report.