(CNN) These first few months of 2019 were supposed to be a slow-but-steady ramping-up of Joe Biden's 2020 presidential campaign, a chance for the candidate and the campaign-in-waiting to build a sense of momentum and inevitability around his not-yet-announced candidacy.

That's not how it's turned out.

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The latest problem for Biden may be a huge one: an allegation by former Nevada state legislator Lucy Flores that he made her feel "gross" and "confused" during her 2014 campaign when he allegedly smelled her hair and kissed her on the head before a campaign rally. Biden on Sunday denied the allegation, saying, in part : "In my many years on the campaign trail and in public life, I have offered countless handshakes, hugs, expressions of affection, support and comfort. And not once -- never -- did I believe I acted inappropriately. If it is suggested I did so, I will listen respectfully. But it was never my intention."

In a vacuum, this is a troubling -- if survivable -- issue for Biden. But he (and we) don't live in a vacuum. The truth is that Biden's familiar approach a) has always been a part of his political persona and b) troubled some not-insignificant group of people who have wondered whether the media was giving the former vice president a pass that they might not give other politicians.

Then there is the fact that we are living in the midst of the #MeToo movement -- and Democrats (especially those running for president) have been particularly outspoken about the need to believe the women making accusations. The simple fact is that what was once accepted as "guys being guys" behavior even as recently as 10 years ago, is no longer accepted. (And shouldn't be!)

Flores, to be clear, isn't suggesting that Biden sexually harassed or assaulted her. But she is suggesting that his behavior -- which he has exhibited publicly for decades during his time in elected office -- made her feel uncomfortable. While that discomfort may be in the eye of the beholder, if even one woman feels the way Flores feels about how the former VP acted around them, it could spell major, major trouble for his campaign.

While this blow-up with Flores is the biggest problem Biden's non-campaign has faced, it's not the only one.

The leak of the fact that some in Biden's circle were considering tapping Stacey Abrams, the 2018 Democratic gubernatorial nominee in Georgia, as his vice presidential pick early in the primary process struck many --- including me -- as a dumb move . It signaled a clear sense of weakness -- old white guy needs young black woman to help him win the nomination -- and seemed hugely premature.

Abrams thought so, too. She made clear in an interview with "The View" last week that serving as VP was not the primary focus of her conversations with Biden and that she might have presidential ambitions in her own right. "If I'm going to enter a primary, then I'm going to enter a primary," she said. "If I don't enter a primary, my job is to make certain that the best Democrat becomes the nominee and whoever wins the primary, that we make sure that person gets elected in 2020."

bolding is mine): Then there are the concerns about Biden's ability to match the likes of Beto O'Rourke and Bernie Sanders in small-dollar, online fundraising. This, from a New York Times piece on Biden's struggles last month , is spot-on (is mine):

"Both Mr. Biden and his top aides question whether he will be able to make deep inroads with millennial voters in a primary, and also whether he will be able to raise large sums of money online.

"Unlike a number of other candidates, such as Mr. O'Rourke and Senators Bernie Sanders, Kamala Harris and Elizabeth Warren, Mr. Biden has not spent years building a muscular digital operation aimed at stimulating online supporters to give money. So his team is mulling a host of unconventional steps, including several related to fund-raising, transparency and the mechanics of a campaign."

Make no mistake: One of the major reasons that Biden didn't enter the race in March was out of concern that if he had a less-than-overwhelming month of fundraising, it could damage the air of invincibility his side is trying to portray. And, because Biden lacks the robust online fundraising operation of the likes of O'Rourke and Sanders, when he does eventually get in the race, he will have to block off more time for fundraising events on his schedule than two of his top opponents.

Look. There still is a forest through the trees. And it shows that Biden, according to every poll worth anything, will enter the race as the frontrunner both nationally and in places like Iowa and New Hampshire. He has done this before -- Biden ran for president in the 1988 and 2008 campaigns -- and knows that one bad day or one bad week do not a campaign make (or break). He has lots of people who will immediately endorse and support him. And on and on.

Even with that big caveat, it's impossible to suggest that these first few months of 2019 have gone according to plan for Biden. I don't think these hurdles keep Biden from entering the race. But I do think they should give him and his supporters significant pause.

Biden is the frontrunner today. But there are clear warning signs that suggest he may not end the race where he starts it.