Much like the presidential race, Democrats were practising their touchdown dance just a month ago because they would soon be winning the Senate. Let's just say that the hubris has moderated.

It wasn’t too long ago that the conventional wisdom about 2016 leaned heavily in Democrats’ favor: Hillary Clinton was in the driver’s seat in the presidential race; Dems were well positioned to reclaim the Senate majority; and there was even some chatter about the House majority being up for grabs.
At least for now, it’s fair to say the conventional wisdom has changed quite a bit. Republican control of the House is a near-certainty; Hillary Clinton’s lead over Donald Trump has been cut in half; and Republicans are increasingly optimistic about holding onto the Senate.
The New York Times’ Upshot, for example, maintains a frequently updated forecasting model showing which party is favored to control the Senate in the next Congress. A month ago, by a roughly two-to-one margin, Democrats were favored to be in the majority. As of this morning, however, according to this model, there’s a 51% chance Republicans will be in charge.
Daily Kos has its own projections, and it too shows the GOP favored to keep its Senate majority. The Huffington Post’s forecasting model tilts even more heavily in the Republicans’ favor.

538.com still gives the Dems a slight edge to win the Senate.

You may have heard elsewhere that the Democrats’ magic number is four seats. But that assumes they hold onto all their seats and win the presidency, and as I hinted at above, that’s not a safe assumption; instead, they’ll require somewhere between four and six seats. Their first problem is Nevada, where they’re defending the seat held by retiring Senate Minority Leader Harry Reid. In theory, Nevada should lean slightly blue in a presidential year, but it hasn’t done so in either the presidential or the state’s Senate race so far; recent polls there show the Republican Senate candidate, U.S. Rep. Joe Heck, slightly ahead of Democrat Catherine Cortez Masto, a former Nevada attorney general. Thus, Nevada is, at best, a tossup for Democrats, meaning that they might require five Republican gains instead of four.

Of the 34 seats up for grabs, Republicans hold 24 of them. This is because six years ago was the massive 2010 GOP wave.
Now they have to defend some seats they never should have won.
So unless the Dems are totally and completely incompetent, they are destined to win back at least a few Senate seats. We are most likely looking at something near a 50-50 split.
I'm looking forward to Russ Feingold getting back in the Senate.

Of course, there is a problem.
It's mid-September and Democrats have had to shift back to rallying their base because of the alarming lack of enthusiasm might effect turnout.
It's still early, but I see the Dems losing a couple close races and failing to win the Senate.