Pretty sure if Republicans are only leading by single digits in North Dakota and Tennesse they're in for a bad night.
Don't be too optimistic now. 538 now gives Dems only a 74% chance of gaining the house, which is less than their prediction for Clinton winning in 2016. If anything I think this sort of hopeless optimism is what keeps dooming the Dems
Remember that at this point in time in 2016, 538 rated Clinton's chances of winning the presidency at over 80%, which is greater than the probably that they currently give to the Republicans retaining the Senate this year. This means that there is still plenty of time for polls to move in the Democrats' direction for the Senate or in the Republicans' direction for the House. Thus, using this logic, if we shouldn't be too optimistic about the Democrats' chances of taking over the House, we should also not be too optimistic about the Republicans' chances of retaining the Senate, either.