This is the biggest day of Congressional mid-term primaries of the 2018 election year, as eight states - highlighted by California's 53 U.S. House districts - hold primaries for the 2018 mid-term elections, the key politcal battleground for the control of Congress under President Donald Trump.

"If you want to be safe, you must go out and get the Democrats the hell out of office," the President said at a campaign rally last week, as he continues to press members of his own party to get out and vote in 2018, knowing that the loss of control of one - or both houses of Congress - could cause him a lot of headaches.

Here are some story lines to look for on Tuesday night:

1. Signs of which party is more enthusiastic. In the first months of the Trump Adminstration, Democrats were clearly more excited about getting out and voting in special elections. The "Blue Wave" is one of their favorite terms, as they talk big about winning back the House. But there are some polling numbers of late which show Republicans rallying around the President, as the generic ballot on which party should control Congress has tightend as well. Also heartening for the GOP is that Mr. Trump is solidifying his support within the Republican Party. That could make more a much more competitive mid-term than maybe the Democrats have been dreaming about in recent months.

2. All time zones covered tonight. From the Atlantic Ocean, to the Gulf of Mexico, to the Midwest, the Mexican border, the Canadian border and the Pacific Ocean, it's an eight state parlay of races to watch for the Congress on Tuesday. Going from East to West - New Jersey, Alabama, Mississippi, Iowa, South Dakota, Montana, New Mexico, and the big one, California. 85 seats in the U.S. House are spread out over those eight states, but 53 of them are in California, making that the late night, Pacific Time focus. I won't recommend staying up late for the California results, but it might be mandatory in November. The other warning is that mail in ballots in California keep those numbers active for days after the election as well.

3. California's "Top Two" primary system. It's important to remember that California is a different animal when it comes to picking candidates for the general election ballot. Instead of separate primaries for each party, everyone is thrown into the same race, and the top two finishers - regardless of party - qualify for the November election. In the House races, that has both parties worried that a divided field might allow one party to grab both slots - that's become a big concern for Democrats in some southern California districts. Three races seem to be the ones to watch for Democrats worried about not getting into the top two, in the 39th (open GOP seat), 48th (seat of Rep. Dana Rohrabacher R-CA), and 49th districts (Rep. Darrell Issa R-CA) in the U.S. House, where a lot of money is being raised and spent by Democratic challengers - but there may be too many of them, and that has Democratic activist worried.

4. Will there be any incumbent surprises? Most of the time, the primaries are simply the battlegrounds to set up key showdowns in Congress for the November elections. So far this year, only one sitting House member has been defeated - Rep. Robert Pittenger (R-NC) has that dubious distinction. In 2016, five incumbents lost, while it was four in 2014. So, one might think that there is someone in the House right now who doesn't realize that their seat is in limbo. Overall, the "casualty list" stands at 54 sitting members of the House who won't be back in January, 37 are Republicans and 17 are Democrats. In the Senate, it's three GOP Senators who won't be returning. If you've been following along with me in recent years, you know that I have been arguing for some time that turnover in Congress is much higher than people realize. To me, it was notable that one Republican said exactly that last week on Twitter (even if our figures differ).