It’s been three weeks since former Vice President Joe Biden swept Sen. Bernie Sanders in major primaries in Florida, Illinois and Arizona, boosting his lead over the populist senator from Vermont in the crucial race for convention delegates to over 300 and cementing his role as the all but certain Democratic presidential nominee.

After those crushing defeats, Sanders said he was “reassessing” his presidential campaign but later stressed that he still had a “narrow path” to win the nomination.

SANDERS SUSPENDS PRESIDENTIAL CAMPAIGN, MAKING BIDEN THE CLEAR PRESUMPTIVE DEMOCRATIC NOMINEE

So why did Sanders pick Wednesday as the day to formally suspend his presidential campaign?

Wisconsin’s primary may have had something to do with the timing.

Sanders easily won the state’s 2016 Democratic presidential primary over eventual nominee Hillary Clinton. But the final public opinion polls before Tuesday’s contest suggested Biden leading the progressive senator by a nearly two-to-one margin.

The results in Wisconsin won’t be known until early next week – following federal district court ruling held up by the U.S. Supreme Court that delayed reporting the results for nearly a week. But a Democratic strategist close to the Sanders campaign suggested that intel how the vote was trending may have contributed to the timing of the senator’s announcement.

The strategist – who asked to remain anonymous to speak more freely – said that “by calling it today, Sanders gets to own the narrative.”

Sanders' announcement also came just a couple of days after the Washington Post reported that his top aides – including longtime political strategist Jeff Weaver and 2020 campaign manager Faiz Shakir – encouraged the senator to end his presidential campaign.

A Democratic operative with ties to Sanders told Fox News, “How do you continue on when you have a campaign manager who apparently doesn’t believe in the cause anymore.”

SANDERS RAISES EYEBROWNS WITH MOVE TO STAY ON PRIMARY BALLOTS, AMASS CONVENTION DELEGATES

In his announcement that he was suspending his campaign, Sanders acknowledged, “We are now some 300 delegates behind Vice President Biden, and the path toward victory is virtually impossible. … I have concluded that this battle for the Democratic nomination will not be successful.”

Sanders emphasized, “If I believed we had a feasible path to the nomination, I would certainly continue the campaign. But it’s just not there. … I cannot in good conscience continue to mount a campaign that cannot win.”

A progressive adviser who’s close to the campaign noted that “the handwriting had been on the wall for quite some time.”

The adviser said that like every decision made by the senator and his wife Jane, “it comes down to what works best for Sanders’ political movement… He’s clearly decided that the best course of action to further the movement was to end the campaign for the nomination.”

Sanders has always stressed that his two presidential campaigns were more than just that – that they were a political revolution.

And on Wednesday, the senator emphasized that “while this campaign is coming to an end, our movement is not….the fight for justice is what our campaign has been about. The fight for justice is what our movement remains about.”

THE LATEST FROM FOX NEWS ON THE 2020 PRESIDENTIAL CAMPAIGN

Sanders was flying high in February – thanks to a partial victory the Iowa caucuses, an outright win in the New Hampshire primary, and a landslide victory in the Nevada caucuses. The candidate zoomed to front-runner status – but it was short-lived.

Biden crushed Sanders and the rest to the still relatively large Democratic field of White House hopefuls in South Carolina, jump-starting his campaign.

The Democratic strategist with close ties to the campaign said that the week leading up to the South Carolina primary – which Biden was expected to win – “was the time to get as many mainstream Democrats and trusted names in the Democratic Party to coalesce around Sanders.”

But the source charged, “The campaign kind of did a victory dance in the endzone for a week instead of really building. I think the campaign really underestimated what a win for Biden in South Carolina would look like and how it would turn the tide.”

Two fellow moderate Democratic rivals – Sen. Amy Klobuchar of Minnesota and former South Bend, Ind., Mayor Pete Buttigieg -- immediately dropped out of the race and endorsed Biden following his Palmetto State victory, which was larger than expected.

While the centrist wing of the party started coalescing around Biden in two days following the South Carolina primary and ahead of the coast-to-coast contests on Super Tuesday, Sanders didn’t enjoy a similar coalescing of the progressive wing of the party – as fellow populist Sen. Elizabeth Warren remained in the race.

Biden ended up taking 10 of the 14 contests on Super Tuesday – growing his delegate lead over Sanders and sparking a tidal wave of support among Democrats nationwide.

“I do think that Warren staying in the campaign through Super Tuesday hurt the campaign because I think if Warren had dropped out before March 3, Sanders would have won Maine, Minnesota,” the strategist predicted.

The day after Super Tuesday, the last remaining moderate candidate – former New York City Mayor Mike Bloomberg – suspended his campaign. A day later Warren ended her bid, essentially turning the Democratic nomination race into a two-candidate showdown between Biden and Sanders.