About a year ago at this time, many of us in Washington, DC were trying to catch our breath, still reeling from the political upset that blindsided us. Many of us were wondering if the rulebook of politics—the one all of us had been dutifully following for years—should be thrown out. A year later, however, with hindsight and our first Trump-era off-year election, it’s clear that the rules were not re-written in 2016 and they remain intact today.

In 2016, voters were given a choice between two deeply flawed candidates with sky-high disapproval ratings. One of those candidates represented the status quo. The other represented change. Voters, as is the case—the "rule" as it were—in almost every election when one party has been in the White House for eight years, picked change over more of the same. They did this even as they knew that the “change” represented a significant risk.

This Tuesday, we saw another law of politics reaffirmed: off-year elections are a referendum on the President. When the president is unpopular voters will penalize his party. If he is popular—or at least not unpopular—voters are less likely to punish his party. Trump is deeply unpopular in Virginia and New Jersey as well as many of the well-educated suburban areas that held elections this Tuesday.

Ed Gillespie was a proxy for Trump. Democrat Ralph Northam was the anti-Trump. It didn’t matter that Gillespie didn’t campaign with Trump. Or that Northam no longer called Trump a "narcissistic maniac" in his ads post-primary. In the end, voters wanted to send a message about the president.

This proxy war on Trump extended all the way down the ballot. Democrats picked up at least 15 seats in the House of Delegates (there are four other GOP-held seats still undeclared as of Thursday). They were expected to gain anywhere from 4-7. That is the official definition of a wave. While some, like the HD13 contest between Democratic transgender reporter Danica Roem and Republican conservative fire-brand Bob Marshall, were highly contested and targeted, a number of others were not. The Democrats were simply in the right place at the right time.

Republicans in Congress should be very worried about that for 2018. Many of them believe that they can simply insulate themselves from a wave by focusing on hyper-local issues and keeping their head down. After all, most over-performed Trump in 2016. The thinking is that they can do it again in 2018. But, of course, unlike 2016 President Obama is not in the White House. And, Hillary Clinton isn’t on the ticket. It’s now all about Trump. If he lost your district in 2016, or is deeply unpopular there, you are going to have a difficult time “localizing” your way out of the mid-term. If Trump’s image and job approval ratings improve, so do your chances. If they don’t, it’s going to be very hard to keep the race focused on the accomplishments of the incumbent instead of the president.

Congressional Republicans, acknowledging the drag of Trump and their lack of legislative accomplishments now argue that a tax cut bill will be the thing that can help keep them afloat in 2018. Instead of a referendum on Trump, they contend that they can keep their race focused on “fulfilling” campaign promises. However, it only matters that you passed something if the thing you passed is popular. According to the latest polling from NBC/Wall Street Journal, opinion of the impending legislation is, at best, mixed. Overall, just 25 percent of Americans said that they thought “Trump’s tax plan” as the question is worded, is a good idea, while 35 percent see it as a bad idea. The plurality of voters—39 percent—don’t have an opinion. But, even among Republicans just over half—54 percent—give it a good rating, while another 38 percent have no opinion. That’s not exactly a rousing level of enthusiasm for an issue that Republicans believe will wake up and inspire their dispirited base. Republicans and their allies are preparing to unleash an unprecedented amount of spending to sell the plan and move those undecideds into “good”. That will take good messaging and lots of discipline.

The other political reality revealed on Tuesday was the structural challenge facing Democrats. Specifically, that their enthusiasm advantage, while impressive, is limited to areas and districts that Democrats already hold – or at least have already carried in previous elections. In Virginia, for example, even with a massive turnout advantage, Democrats were only able to flip one legislative seat carried by Trump. All the others were carried by Clinton. Moreover, if you look at the state by congressional district, Northam only carried one GOP district—the Tidewater-based 2nd CD—that Clinton did not win in 2016. Even so, this should not make Republicans all that comfortable. Trump narrowly carried VA-02 by 3 points, 48 percent to 45 percent. Northam carried it by four points, 51 percent to 47 percent. That’s a swing of seven points between 2016 and 2017. If Democrats were able to swing other districts Trump narrowly carried by seven points, they’d be able to pick up more than enough seats to take control of the House in 2018.

To be sure, it’s easy to "overlearn" the lessons of any election. This is especially true when the most high-profile races took place in states that are already deep blue (New Jersey), or light blue (Virginia). Even so, politics isn’t magic. And, even Donald Trump and Republicans can’t escape the laws of political gravity.