It is going to be a long night. My best guess is that Clinton will beat Trump in the popular vote by 3 points, 48.5 - 45.5 with Johnson and Stein getting 4% and 2%, respectively. The electoral college could very well end up being a squeaker with Clinton beating Trump 288-250. Why so close? If I am right about Clinton's 3 point margin, which is somewhat above the polling averages, then California will account for the entire margin of victory. Using simple math with Clinton carrying California by 20 points and California accounting for about 15% of the popular vote; then by simple multiplication you get 3 points. That means the rest of the country will be tied.
How I get to 288 for Clinton is that I give her Nevada and Florida, but I give Trump Ohio, North Carolina and in two upsets I give him New Hampshire and Michigan. Question: why are Obama, Hillary and Bill visiting Michigan tomorrow? Trust me, it is not for the mid-Fall weather.
As far as the Senate goes, with Trump not collapsing the GOP has a real chance to hold on. There are going to be more than a half dozen very tight races so the margin for error is large. My central tendency is for the Republicans to hold the Senate by a razor thin 51-49 majority. The only sure loser the Republicans have is Mark Kirk in Illinois. Now if Clinton wins by 5 points, the Democrats will take the Senate by something like 52-48.
As far as the House goes it now looks like my fears of a few weeks ago that the Democrats would take the House were unwarranted. Again assuming a 3 point victory for Clinton, the Republicans figure to lose about a dozen seats ending up with a 234-201 majority. And because the Republicans are the "stupid" party they will immediately squander their victory by having a leadership fight. A fitting coda for the ongoing collapse of a party that had victory on a plate and it nominated the only candidate that could lose to Clinton.
Correction and Addendum
California accounts for 10% of the vote not 15% as stated above. Thus with Clinton carry California by 20 points her margin of victory in the rest of the country would be 1 point. Not zero, but very close. In 2012 President Obama beat Romney by 5 points with 2 of those points coming from California. Thus if his margin of victory was only by three points with California being roughly unchained, we might now be witnessing Mitt Romney's reelection campaign.