The holiday dinner conversations are going to be intense in several high-profile Democratic households in the coming weeks, as potential candidates near decisions on whether to run for president in 2020.

Even as their staffs and political advisers have already begun scouting out office space, interviewing potential aides, and plotting out strategy for the 2020 presidential election, most haven't completely made up their minds about entering what's expected to be one of the most crowded primary contests in history.

"I don't know, and I still don't know," former Vice President Joe Biden told reporters on Election Day. "It will be a family decision, and we have time."

Not too much time, though.

Some candidates view Thanksgiving as the start of the window for making the political and personal calculation to go forward with or take a pass on a run for the White House. Given the likely size of the field, as well as the extended timeline of presidential campaigns, most of the top-tier potential candidates acknowledge they'll have to decide by the end of December, if not sooner.

NPR has interviewed key advisers to nine potential presidential candidates in the days since the midterm elections. Most of the conversations were conducted anonymously, so staffers could speak openly about politically sensitive matters.

Here's a glimpse at the potential 2020 Democratic presidential field:

Senators

Representatives

Governors

Others

The fact that that isn't even the full list of potential candidates speaks to the fact that, with a first-time candidate from the world of reality television in the Oval Office, all previous notions about paths to the presidency have gone out the window.

But it also underscores Democratic optimism about the party's chances in 2020.

Lessons from 2018

Tuesday's election results only confirmed that confidence. Democrats gained more House seats than in any election since the 1974 wave after Watergate, in addition to their statehouse wins and holding down their losses in the Senate, which included flipping GOP seats in Nevada and Arizona.

The political operatives preparing for presidential runs all see last week's outcome as a signal that President Trump would be a vulnerable opponent in two years.

"Trump became president because he lost the popular vote, but he won the Electoral College in states like Pennsylvania, Ohio, Michigan and Wisconsin," Sen. Bernie Sanders, I-Vt., told NPR. "Well, three out of four of those states elected Democratic governors, and all four of those states elected Democratic United States senators. So I think Trump's victories in those very important states may not be longstanding."

Advisers to nearly every other potential Democratic candidate agreed with Sanders on Pennsylvania, Michigan and Wisconsin, though many expressed concern about both Ohio and Florida – two perennial swing states that have trended increasingly Republican in recent years.

That was tempered by optimism about the Democratic Senate win in Arizona, as well as tight races in other Republican strongholds like Texas and Georgia.

One operative compared the Democrats' margin in the national House vote — approaching 7 points — to Hillary Clinton's two-point margin in the 2016 popular vote. "It's a meaningful indication of [Trump] weakening," the adviser told NPR. "When you won the presidency by 80,000 votes, this does not bode well." (That's the rough combined total of Trump's margins in Wisconsin, Pennsylvania, and Michigan – the three reliably Democratic states Trump peeled away to win the Electoral College.)

In addition to Democrats winning the House, "Republicans had the most advantageous Senate map since 1914 and may end up with a net of two [senators added to their majority]" said another adviser in a different likely campaign. "Talk about underperformance."

"For 2020, it is very positive news that Democrats were able to win statewide re-elects in some of the Midwestern states we lost last year, that would help them get to 270," said Jen Palmieri, a senior aide to 2016 Democratic nominee Hillary Clinton. "And I think that that's the message there — you need to have a progressive agenda that's going to offer solutions for real problems people face. But you need to present this in a way that is going to unite people and bring them together, not further divide."

What's the best strategy?

Does that mean a moderate, bridge-building candidate would fare better than a high-profile Democrat who has made national headlines already going toe-to-toe with Trump? Is the answer appealing to the Democratic Party's base, or offering a moderate, even boring Democrat whom independents and Republicans tired of Trump could feasibly support?

Ultimately, Democratic primary voters will decide.

Another key question, albeit a question that doesn't need to be decided for some time: whether to focus a general election on retaking those Midwestern states, or challenging Trump in Arizona, North Carolina and other Democrat-trending Sun Belt states.

That's where campaign staffers-in-waiting begin to draw different conclusions from last week's results. The more progressive and aggressive camps see Beto O'Rourke and Stacey Abrams' performances in Texas and Georgia as a sign that base mobilization can turn a Republican state blue with two more years of organization and demographic changes.

The more consensus-minded camps – notably, including most of the potential candidates who aren't based in Washington – are more apt to focus on the fact that Democrats flipped the House by running moderate, sometimes cautious candidates who fit their district profiles, which is also how Sen.-elect Kyrsten Sinema ran in Arizona.

But as more and more Democrats have embraced progressive positions like a $15 minimum wage, the main choice may come down to a matter of tone and framing. Do you run a campaign attacking Trump, or trying to appeal to the middle and win over wary conservatives?

In short, it's the difference between the mindset that New York Sen. Kirsten Gillibrand laid out on The Late Show With Stephen Colbertlast Thursday night, and what Montana Gov. Steve Bullock spelled out on MSNBC's Morning Joethe very next morning.

Gillibrand told Colbert she sees 2020 as a clear, black-and-white divide between good and evil. "I have seen the hatred and the division that President Trump has put into our country," she told Colbert, "and it has called me to fight as hard as I possibly can to restore the moral compass of this country."

Bullock opted for a far more conciliatory approach: "As much as we can bridge some of these divides, and as much as we can make people have a reason to believe government can work in a broken political system, that matters."

Over the coming weeks, staff will keep working behind the scenes to lay the groundwork in case they do run. Gillibrand, Harris and Sanders will all field questions about their potential candidacies while promoting new books hitting stores this holiday season.

But all of that preparation will remain potential, until each candidate makes the deeply personal decision of whether to launch a process that could irrevocably reshape their lives, win or lose.

NPR's Asma Khalid contributed to this report

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