First, President Trump can choose to not change his stripes and remain the confrontation, base-focused president he's been. The up side to that is he gets to continue his story-line of “us versus” them as he begins his re-election campaign, and can point to the Democratic House as the reason nothing gets done in Washington.
Soon-to-be-Speaker-again Nancy Pelosi then needs to determine her strategy which at the moment looks to be strong but not overly threatening – she’s taken impeachment off the table for now, a smart move since impeachment will not succeed with a GOP Senate and it would set the wrong tone for the House Democrats right now.
She has the power of the investigation and subpoena to wield against Trump, a Washington he has not experienced before, a Washington where his Cabinet will be on the Hill often to testify and justify what they did and how they did it. Those investigations, even if they prove nothing, have a way of drowning a Cabinet member and his or her staff in paper and questions, sucking up the time for anything much else.
Prognosis for the country: continued Washington stagnation which Trump will see as good for him since he is so base- and self-focused. In this scenario a more traditional president would look to foreign affairs as his focus where he needs to worry less about the Congress backing him.
With Trump though it seems like there is trouble in his North Korea efforts, the Khashoggi issue remains with the Saudis, China is smugly ignoring him, the Europeans, well, we all know how his efforts to make them our enemies have been going.
Second, President Trump decides to stay his transactional self and moves to play nice with House Democrats so he can actually accomplish something as he heads toward his reelection effort.
There are things he and Democrats can agree on: infrastructure, which also was there for his taking when he began his presidency; health care, where he’d have to reverse course on some matters to get to agreement, but we know he has no trouble switching positions on a dime. This would tick off the Republicans, of course, but when has that worried Trump?
To take that more friendly approach with House Democrats, he’d have to convince himself his base truly would be with him even if he shot someone on Fifth Avenue but he seems capable of working that magic.
Trump and the Republican Party have another challenge to think about. As my wife, former Boston Globe and CNN political reporter Chris Black, likes to point out: the Republicans are on the wrong side of the future of America demographically.
Yesterday saw, on the Democratic side, big wins for women as they won many more seats in the House; they also won seats with female Muslim candidates, and the black and Hispanic vote likely went heavily Democrat as did the suburban, educated, white female vote. As we go through the “browning of America,” Republicans likely won a majority of over 65 white votes, not a growing demographic.
Trump, though, is a short-term thinker. While the GOP needs to worry about branching out to a wider swath of voters (which they've needed to do far before Trump) for it to compete in the future, Trump will be thinking only about his election, and he is unlikely to attract those voters. Even if he tried, they would see through his hypocrisy. Thus, the party and Trump will be bumping heads over where to spend its resources, and Trump likely wins that argument to the long-term detriment of his party
Trump also wants to almost immediately begin staging more rallies, where he feels in control, loved and powerful and, most importantly, the center of attention. To maintain his popularity among that crowd he can’t waver too much from his first two years even if he wants to. Clearly, he needs to keep his base intact for his reelection and hopping into agreements with the House Democrats won’t win him any votes with that crowd, especially since it would mean making nice to Nancy Pelosi.
So, while the overall numbers yesterday were at best a split victory between the GOP and the Democrats, the takeover of the House by Democrats is a major change for the next two years on many levels and creates a list of sensitive, strategic decisions to make on both sides.