Dana Milbank sums it up well in in Washington Post column:

To Trump’s many self-assigned superlatives, he can now add another: the sorest winner. With charity for none and with malice toward all but his supporters, he has in the past two months set a new standard for gracelessness in victory.

America has never before had such a prickly president-elect, nor one with such a sour disposition. You don’t have to be a shrink to see that Trump’s extreme defensiveness can be attributed to his titanic insecurities. Having lost the popular vote by nearly 3 million, his tweets and vents provide a textbook case study of a man living his fear that his fraudulence will be found out. He follows each new outrage with another, in hopes that his shell game will continue to distract the media, and so far it has worked.

As the winner of the Electoral College vote, however, as President-elect of the United States and leader of the Republican Party, you would think he would be smart enough to extend the hand of friendship to his adversaries, to reach out and at least make noises about bringing Americans together. Just the gesture would probably get him an upward bump in his approval ratings.

Somehow, that obvious, no-downside strategy has eluded him. Milbank elaborates on Trump’s increasingly sour disposition:

Instead of brushing off criticism, as a president-elect can afford to do, Trump in recent days marked Martin Luther King weekend by telling off civil rights icon John Lewis (a King acolyte) and his “falling apart” and “crime infested” congressional district. He bemoaned “Saturday Night Live” spoofs as a “hit job” and used the words “crap” and “sleazebag” in his public statements. He called the top Democrat in the land the “head clown” and accused the American intelligence community of acting like Nazis.

He responded to criticism from Meryl Streep by calling her an “over-rated” actress and a “Hillary flunky who lost big.” He likewise cheered that his “Celebrity Apprentice” replacement Arnold Schwarzenegger got “swamped” in ratings compared with “the ratings machine, DJT. . . . But who cares, he supported Kasich & Hillary.” Trump said the Russian hacking of the Democratic National Committee is discussed only because “the loss by the Dems was so big that they are totally embarrassed!”

The losers often have hard feelings after elections. But this much enmity from the winner is extraordinary. Trump, after his election-night promise to “bind the wounds of division” and be a “president for all Americans,” never attempted reconciliation. A day later, he falsely condemned “professional protesters, incited by the media,” and at year end he taunted opponents via Twitter: “Happy New Year to all, including to my many enemies and those who have fought me and lost so badly they just don’t know what to do. Love!”

…His behavior during this time has not been what one typically calls presidential. He has echoed both Vladi­mir Putin and WikiLeaks’ Julian Assange on Twitter and blasted away in all caps. He attacked Vanity Fair magazine editor Graydon Carter after an unfavorable review of a Trump Tower restaurant. His attack on a local steelworkers union president resulted in death threats.

 Trump has used Twitter to attack everything from the “Hamilton” musical to the Chinese government, and, in one tweet, he appeared to commit the United States to attacking North Korea to prevent it from developing a nuclear weapon capable of reaching the United States.

There is no slight too trivial for the GOP’s new leader to ignore. He has a singular genius for converting a one-day story into a 3-day pubic relations disaster. That probably helps explain why his “favorability” rating has tanked in a recent Quinnipiac University poll.  As Milbank notes, “Views about his honesty, leadership and ability to unite the country dropped similarly.”

Jennifer Calfas reports at The Hill:

The ABC/Washington Post poll found that 54 percent of Americans view Trump unfavorably. The unfavorable ratings of former Presidents Jimmy Carter, Ronald Reagan, George H.W. Bush, Bill Clinton and Obama ranged from 9 to 20 percent when they entered office. The new poll echoes similar ones produced from CNN and Gallup.

A CNN/ORC poll also released Tuesday also found Trump had a 40 percent approval rating — a historically low number for a president-elect.

A Gallup poll released over the weekend found similar numbers, with Trump’s favorables historically low.

Trump’s propensity for the endless, nasty gloat may gratify some of his angrier supporters, and he clearly gets off on the feedback they provide at rallies. But how well does it serve his party’s prospects in the 2018 midterm elections? He’s already won a large majority of America’s sourest voters. There is no value added in marinating in bile for him or the Republicans, but that isn’t going to stop him from taking the bait every time.

All of this in stark contrast to outgoing President Obama, who gave Americans a new standard of dignity, grace and scandal-free government, as well as economic recovery, and greater health security. The new Gallup poll reports that President Obama leaves the White House with a 58 percent ‘favorable’ rating.

Despite the daunting landscape Democrats are facing in the 2018 senate races, their competitive position with respect to House races, governorships and state legislatures is improving. If Trump continues his daily temper tantrums, the GOP ‘brand’ could be in serious trouble by November, 2018.