WASHINGTON — Joe Biden may not be ready yet to tell Americans if he’s running for president. But starting with appearances this week in front of two supportive audiences, he’s about to start telling them why.

For the first time since the midterm elections, the former vice president will headline a pair of political events that may serve as a final test drive of the message he could take into the 2020 campaign, one advisers say balances a bold agenda focused on reviving the middle class with an appeal for moving beyond the smallness in our politics.

Underlying Biden’s pitch is the urgency of defeating a president that he feels has governed at odds with America’s values — framing the next election as a “battle for the soul of America,” as he has put it.

It begins Tuesday when Biden addresses the International Association of Firefighters for what could amount to a pre-emptive endorsement event.

“You’re going to see, ‘Run Joe Run,’ the gold and black ‘Firefighters for Biden,’” IAFF General President Harold Schaitberger told NBC News on Monday. “We’ll be doing everything to show where we stand. And then, it’s up to him to make his final decision."

Advisers insist that Biden still hasn’t made one. He and his wife spent last week on what may well have been a final pre-campaign vacation in St. Croix, ahead of an informal deadline that his team had set as the goal for getting the green light to execute the campaign plan long in the works.

No final decisions have been made about what would be the campaign platform, either. But advisers say the starting point would be what they sketched out as he considered entering the 2016 race.

The 2,500-word announcement speech that Biden never ultimately delivered promised voters a campaign based on the principle of “one America, bound together in this great experiment of equality and opportunity,” where “everyone — and I mean everyone — is in on the deal.”

Among proposals Biden is again considering for 2020 are:

A tax code overhaul to treat investment income as earned income, changes that would help pay for free community college.

A $15 per-hour minimum wage.

Free tuition at public colleges and universities.

A major “American Renewal Project” to rebuild the nation’s infrastructure.

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In 2018, Biden focused often during campaign events on the need to protect and improve on the Affordable Care Act, but he has yet to embrace “Medicare for All,” an emerging litmus test for Democratic candidates.

On another front, Biden has said he is prepared to reject the support of a super PAC to boost his candidacy — surrendering what would be a potential advantage in the crowded field given his longstanding ties to major Democratic donors. Super PACs are political action committees that can take unlimited contributions from wealthy donors, but they may not coordinate with the campaigns.

Make or break moment

Biden may well sound like a candidate this week when he addresses the two very friendly crowds: Tuesday at the International Association of Firefighters, and Saturday at a Delaware Democratic Party dinner in Dover.

Tuesday’s IAFF conference will look and sound a lot like an endorsement event. In past presidential cycles, the union invited multiple candidates in both parties to address its members. But this year, Biden was the only candidate or potential candidate to score an invitation.

Schaitberger said that while Biden is not officially a candidate, he sees the delay "as more strategical about the timing of a likely announcement than maybe the actual decision on whether to announce.”

“I’d be very surprised” if he didn’t run, he said.

Biden’s uncertain plans remain the single biggest variable in a Democratic primary fight that has been waging in earnest now for two months. But according to conversations with aides familiar with the discussions, even most in Biden’s orbit who had believed he could pass on the race now say they would be surprised if he doesn’t run.

His team has recently impressed upon him the timeline needed to prepare for a campaign launch in early or mid-April. While no campaign jobs have been formally offered, discussions underway for months with potential staff have gone from theoretical opportunities to specific roles, following Biden’s instructions that his campaign team “reflect the country” with diversity in senior roles.

The coming week may be a point of no return for him, as aides recognize that the party’s patience is wearing thin. To the extent advisers identify any potential hurdles he’s still reckoning with, they are parallel: how and when to engage with attacks from the most strident partisan voices in both parties, including Trump.

Even as Biden will tout a bold agenda, he has stressed the need for both parties to be willing and able to forge compromises when in the public interest.

“Our job is to restore dignity to the political discourse, and restore the basic bargain in America,” Biden said at an appearance in Iowa, last October. “The only thing that’s strong enough to tear America apart is America itself.”

It’s a message seemingly at odds with a vocal cohort in the party that sees any form of accommodation with Republicans as disqualifying. Biden was pilloried for calling Vice President Mike Pence a “decent guy,” even though it came in the context of drawing a sharp contrast with the administration’s foreign policy. In January, he forcefully pushed back at criticism of his praise for a vulnerable Republican congressman just weeks before the midterm elections.

“I don't know how you get anything done unless we start talking to one another again,” he said then.

That message still didn’t sit well with the key voices in the base.

“Declarations of, ‘Oh, we need to get back to doing bipartisan things,’ it’s just not the era that we’re in,” Rep. Pramila Jayapal, D-Wash., co-chair of the House Progressive Caucus, told NBC News recently. “We have to understand the threat that our democracy is in, and not romanticize some notion that really isn’t relevant to where we are today.”

Biden’s team says there is ample evidence that more primary voters share his outlook, and that he could have the broadest appeal in a race against Trump. In 2018, Biden appeared in support of 16 Democrats who flipped GOP-held House seats, and four who won back GOP-held governors’ mansions, in states such as Pennsylvania, Wisconsin and Michigan that carried Trump into the White House.

Public polling suggests that Democratic voters, for now, are more interested in backing a candidate who can beat Trump than someone who lines up with them on issues. And a January poll from the Pew Research Center found that among Democratic and Democratic-leaning registered voters, 53 percent wanted the party to move in a more moderate direction than more liberal.

“You’ve got a number of candidates chopping up that particular space on the extreme left end of the political spectrum," former Florida Sen. Bill Nelson said in an interview. "There is a good part of the left of center that, if he runs, Joe will occupy. And that puts him in the best position in a general election to win the presidency.”