Dems don't have the votes to take control of Senate at this point

The Hill:

The campaign chairman for Senate Democrats on Wednesday warned his colleagues that if the elections were held today, the party would gain only three Senate seats, according to lawmakers who were in the room.

That outcome would leave Democrats one seat short of the majority, should the party’s presidential nominee, Hillary Clinton, win the White House.
...
While Senate Democrats have a favorable electoral map, they say a deluge of spending from outside groups has buoyed vulnerable Republican incumbents such as Sen. Rob Portman (Ohio), who had been a top target.

The DSCC and Senate Majority PAC, a Democratic super PAC, recently canceled advertising buys in Ohio.

Tester sees Illinois, Wisconsin and Indiana as three slam-dunk races for the parties. But other states — New Hampshire, Pennsylvania, Florida and Ohio — are turning out to be much tougher than anticipated.
...

Portman is so far ahead that GOP groups have also quit spending in Ohio to concentrate on other races.  With Trump having so much trouble, the GOP donors are focusing on winnable races to keep control of the Senate.  The Koch brothers are also spending heavily in Nevada trying to flip the seat currently held by Harry Reid.