In 2012 there were 129,237,642, down from 131,473,705 in 2008. That was a surprise because there were more American 18 years or older in 2012 than in 2008. I predict that we'll see a good bump in 2016 with the electorate over 140 million. Turnout looks strong in early voting and there appears to be enthusiasm on each side.
Donald Trump will improve over Mitt Romney in Northeastern and Midwestern states where Barack Obama did well with working class white voters. Some of these voters will turn to Donald Trump. I predict that Trump will see his biggest in Rhode Island. Barack Obama won the state by 27.5%. Donald Trump will lose the state by double digits but the gain will be big. Other states where Trump will make big gains are New York, Maine, Iowa, New Jersey, Connecticut, and Michigan. Unfortunately, the only state Trump might win is Iowa, although he has a shot at Michigan.
For years Republicans have been winning 80-90% of white voters in southern and some western states. There are no working class white voters voting Democratic. But there are plenty of suburban white voters voting Republican. Trump is a turn off to some of them. In other states working class whites might offset are even more than offset losses amongst these voters. South Carolina, Arkansas, Idaho, Georgia, and Tennessee should be states where Hillary Clinton will make the biggest gains. She is unlikely to win any of these states but has a chance at Georgia.
Don't be surprised if polling is off. While polling was pretty good in the primaries it wasn't in the 2012 and 2014 elections. The electorate this year is likely to be different than previous ones. Will there be a Latino surge? If so, how much of one? Are the missing white voters working class Trump supporters who'll show up this year? I'm not going to predict whether the polls are wrong for Republicans or Democrats but that they are off.
The state expected to be the tipping point state won't be. So many states are polling within 4% that no one can predict which one will be the closest. There are some early states to watch, however. Ohio, Florida, Georgia, Virginia, and South Carolina all close at 7 or 7:30 PM eastern. (Part of Florida closes at 8, but the networks might not wait there) If the margins are better for one candidate in these states then that candidate might be surprising. Exit polls are usually, but not always accurate, and don't get fooled by vote counts like Karl Rove did in 2012. Mitt Romney was close enough to win Ohio when Fox called it for Barack Obama, but a disproportionate number of the remaining votes were from the city of Cleveland. Obama ran up big margins there and he did win comfortably.
The Senate isn't always a sign of a wave, but the House is. Every cycle there are expected to be around 10 states that are close. If one party wins a good percentage of them it may be because of good candidates or other state circumstances. The sample size is so small that a few breaks could turn a 5-5 split into a 9-1 advantage. I'm predicting that Wisconsin, Illinois, and Pennsylvania flip to the Democrats and the Senate will be 51-49 Republican. I wouldn't be surprised, however, if either party does several seats better.
The House is 435 elections. Some of them are going to be big romps no matter what but environment impacts most of them too. A candidate that'd normally win 67%-33% might win 64%-33%. So while the Senate might go big one way or the other the House definitely won't. I'm predicting the Democrats pick up 11 seats, FL-10, FL-13, IL-10, MI-1, MN-2, NH-1, NJ-5, NV-3, NV-4, TX-23, and VA-4. Republicans will pick up 3 seats, FL-2, FL-18, and MN-8. That'd net Democrats 8 seats and put the Republican advantage at 239-196. Democrats might do better but even if they do, they won't exceed 205 seats.