Hillary Clinton has raised $18 Million for the DNC and state parties, money that is commonly referred to as a "victory fund." The assumption is that all of this money will go toward helping "downballot candidates" but that is not necessarily true.
During the primary campaign, donors are limited to $2,700 in direct contributions to the candidate. To elicit larger contributions from willing donors, a candidate can set up a Joint Fundraising Committee which allows donors to cut one check that gets distributed to the candidate as well as a state party and the national party. The first $2,700 goes to the candidate's campaign, and any additional money can go to the state party ($10,000 limit) and the national party ($33,400 limit). Clinton's campaign has so far raised $18 Million for the national and state parties.
However,
There is nothing stopping the state party from using the money to help the eventual nominee
Could that $18 Million be spent on helping Hillary's campaign? At least part of it can. I was unable to find out if that same lack of restriction also applies to the national party which receives the bulk of the JFC money.
It's also possible that some of that $18 Million could be spent on Bernie Sanders' campaign, should he win the party's nomination.
One could speculate that the closer the presidential race is between the Democrat and the Republican, the more likely it would be for these funds to go toward the presidential candidate rather than the downballot candidates. So the candidate who trails or only has a slight lead against the Republican might end up sucking away a portion of the victory funds otherwise meant for the downballot candidates. I'll leave it to the reader to interpret the polling of potential matchups and draw their own conclusions as to the various scenarios regarding the likelihood of that money being spent on the presidential candidate.