WASHINGTON D.C. — Michael Bloomberg seemed to be moving towards a run for president. The former New York Mayor was hiring staff, making trips to early voting states, and his team was thinking big about a nationwide strategy that would be funded by his billions.

But on Tuesday, Bloomberg opted out, saying in an op-ed that he was “clear-eyed about the difficulty of winning the Democratic nomination in such a crowded field.”

After an initial burst of Democrats joining the presidential race, decisions this week by Bloomberg, Oregon Sen. Jeff Merkley and Ohio Sen. Sherrod Brown signal how other would-be candidates are shying away from the race – and in some cases it’s less about the size of the field, and more about who is still likely to be in it.

Sources close to Bloomberg say that former Vice President Joe Biden’s potential entrance into the 2020 fray made an uphill, but potentially winnable, primary slog even steeper for the New York billionaire. While Bloomberg’s path to the nomination was narrow already, “the path is really narrow with Joe in the race,” one source close to Bloomberg told NBC News, speaking on condition of anonymity so as to speak more candidly

Bloomberg will turn next to building out a general election apparatus for Democrats before the eventual nominee even hits the general election, as well as continuing to focus on a Beyond Carbon initiative to push America toward clean-energy.

Bloomberg and Biden spoke this week, after the former mayor announced his decision. Biden advisers said they were not aware of any conversations between the two since they spoke at an event together in January; members of Bloomberg’s inner circle were guided by tea leaves in the former vice president's recent appearances, leading them to the conclusion that Biden will ultimately jump into the race.

Brown, who announced Thursday he would not run, told reporters that while he and Biden have spoken from time to time, “his getting in or out had zero impact” in his decision. But he said Biden is among those potential candidates who could carry his “dignity of work” message in the election. 

Though Biden and his team are signaling that his default position is to run, no final decision has been made. The former vice president said publicly last week he was in the “final stages” of a final call, and that he was now confident his family on board – a key factor for any potential candidate, but especially so for Biden. Deliberations are now instead focused on the very question Bloomberg wrestled with: can he win the nomination?

Biden’s public appearances of late have been limited and largely non-political. That changes next week with speeches Tuesday at the International Association of Fire Fighters, and Saturday before the Delaware Democratic Party – two bedrock political constituencies for him over the years. 

Biden now is on what could be a final pre-campaign vacation with his wife in St. Croix. Two strategists who have been close to the planning insisted that no green light has been given yet, and therefore no staff has been formally hired. But regular conversations with potential hires that have been under way for months are becoming more definitive.

They’re not the only ones left waiting on Biden. Jennifer Clyburn Reed, the daughter of longtime Congressman Jim Clyburn, D-S.C. and someone who has been showing multiple 2020 hopefuls around the Palmetto State, says there’s “still a little time left” to mount a bid — but voters are hungry for options.

“If you’re going to run, get in here so we can start looking at our choices,” she told a small group of reporters in Columbia, South Carolina in February when asked about Biden, and others who haven’t jumped in yet. Likening the crowded field to a buffet, she cautioned with a laugh: “Don’t bring out the macaroni and cheese after all the main dishes are gone. I would really like to see my meal all out at once” before picking the “main course.”

—Garrett Haake contributed