washington <u+2014> standing in the rose garden, where he once marked the paris climate accord, celebrated the supreme court decision saving his health care law and unveiled the iran nuclear deal, president obama promised on wednesday to <u+201c>root for<u+201d> donald j. trump , even though mr. trump has vowed to topple those and other pillars of mr. obama<u+2019>s legacy. <u+201c>everybody is sad when their side loses an election,<u+201d> the president declared. <u+201c>but the day after, we have to remember that we<u+2019>re actually all on one team. this is an intramural scrimmage.<u+201d> for mr. obama, however, this scrimmage could result in the reversal or dismantling of several of his most cherished achievements <u+2014> laws and agreements that required years of negotiation, heavy doses of political capital, and, in some cases, a stroke of luck. the white house acknowledged that mr. obama<u+2019>s signature legislation, the affordable care act, was in genuine jeopardy. mr. trump has vowed to repeal it as one of his first acts in office, and a republican-controlled congress will prod him to do so. josh earnest, the white house press secretary, said mr. obama would lobby mr. trump to keep it in place <u+2014> an effort that suggests mr. obama believes that mr. trump can be persuaded on certain issues. the president invited mr. trump to visit the white house on thursday, and in his remarks, mr. obama struck a conciliatory tone toward his successor. <u+201c>we all want what<u+2019>s best for this country,<u+201d> he said. <u+201c>that<u+2019>s what i heard in mr. trump<u+2019>s remarks last night. that<u+2019>s what i heard when i spoke to him directly. and i was heartened by that.<u+201d> mr. obama also said he <u+201c>could not be prouder<u+201d> of hillary clinton. but as the white house absorbed her defeat and cranked up the machinery to transfer power to mr. trump, there was an undercurrent of anger among his allies that she had squandered the opportunity left to her by a popular president. <u+201c>president obama, with an approval rating above 50 and an unemployment rate below 5, did all he could to set the table for a democrat to succeed him,<u+201d> said dan pfeiffer, a former senior adviser to mr. obama. <u+201c>barack obama will go down in history as one of america<u+2019>s most consequential presidents,<u+201d> mr. pfeiffer added. <u+201c>tuesday is a bitter pill to swallow, but it won<u+2019>t change that fact.<u+201d> the president<u+2019>s remarks capped an emotional day at the white house. dozens of staff members spilled into the rose garden to applaud their boss. just before he spoke, mr. obama pulled a handful of aides into the oval office for a pep talk. earlier on wednesday morning, several had cried during the daily senior staff meeting. as night fell, mr. obama welcomed current and former members of his cabinet to the white house for a thank-you party that was supposed to have been a celebration of mrs. clinton<u+2019>s victory and his administration<u+2019>s work. instead, it was a gathering of stunned officials, and an aide said mrs. clinton would not attend. for weeks, mr. obama campaigned like a happy warrior for mrs. clinton. but asking people to vote to preserve his legacy was less effective than asking them to vote for him. some former officials held out hope that the president<u+2019>s health care legacy could be preserved, saying that mr. trump would hesitate to deprive 20 million people of health insurance without any substitute, and that republican lawmakers, having spent more time trying to scrap the existing law than shape a new one, have no consensus on a replacement. new presidents are often less zealous in unraveling their predecessors<u+2019> achievements than in vowing to do so on the campaign trail. richard m. nixon left lyndon b. johnson<u+2019>s great society legislation largely intact; ronald reagan, after defeating jimmy carter, did not kill off the education department. <u+201c>by the time people go after these institutions, they have constituencies of their own,<u+201d> said robert dallek, a presidential historian. he added, <u+201c>given the impulsiveness and the way he goes from pillar to post, it<u+2019>s impossible to predict what trump will do.<u+201d> mr. trump could undermine a major part of the health law by directing the justice department to alter its position in a lawsuit filed by house republicans. at issue in the litigation are <u+201c>cost-sharing subsidies<u+201d> that help pay doctor and hospital bills for millions of lower-income people. a federal district judge has already ruled against the administration, finding that congress never appropriated money for these subsidies. republicans will not have a 60-vote majority in the senate, so they could not overcome a filibuster by democrats trying to preserve the law. but republicans could dismantle other elements, including the expansion of medicaid , using a budget procedure known as reconciliation, which does not require a supermajority. congress approved such a reconciliation bill in january, which mr. obama promptly vetoed. the president<u+2019>s big international agreements face a similarly perilous future. if mr. trump were to pull the united states out of the paris climate accord <u+2014> which he has vowed to do, labeling climate change a <u+201c>hoax<u+201d> <u+2014> the agreement to reduce carbon dioxide emissions would remain legally binding on the united states for four years, but it would lose much of its impact. mr. obama<u+2019>s mammoth asian trade deal, the trans-pacific partnership, was in political trouble even before the election. now, analysts said, it is unlikely to ever get a vote. mr. trump has said he would have struck a better nuclear deal with iran, suggesting he might try to reopen talks. but four other countries also signed the deal, and there is no sign that they would go along with him. reopening negotiations could also prompt iran to restart its uranium centrifuges, putting the country back on a path to a nuclear weapon. but the iranians have been unhappy with the existing deal because the united states has not lifted direct sanctions, chilling foreign investment. that could provide mr. trump with an opening, experts said. <u+201c>reopening the agreement means reopening it for the iranians, too,<u+201d> said martin s. indyk, executive vice president of the brookings institution. <u+201c>given that they<u+2019>re more unhappy with it than we are, president trump may discover there<u+2019>s more in this deal for our side than he first realized, especially if the alternative is that the iranians restart their nuclear program .<u+201d> mr. obama and his top advisers have always recognized the fragility of his legacy items, especially those achieved by bypassing a recalcitrant congress. after all, the president himself began plotting almost immediately after winning the white house in 2008 how to accomplish his campaign promises, which included rolling back some of george w. bush<u+2019>s policies. during mr. obama<u+2019>s transition, his advisers consulted a book, <u+201c>with the stroke of a pen,<u+201d> which documented the use of executive orders throughout american history, and compiled a set of actions the president could take on his own. now mr. trump is likely to do the same, said gregory b. craig, mr. obama<u+2019>s first white house counsel, who led that process during his transition. <u+201c>during the first 100 days, the presidency will likely become a vehicle for moving the republican agenda forward,<u+201d> mr. craig said. <u+201c>nothing with obama<u+2019>s name on it is safe. it will be: <u+2018>let<u+2019>s pull out the list of obama<u+2019>s sacred cows and slaughter them, one by one.<u+2019> <u+201d> robert pear and gardiner harris contributed reporting. follow the new york times<u+2019>s politics and washington coverage on facebook and twitter , and sign up for the first draft politics newsletter . a version of this article appears in print on november 10, 2016, on page p13 of the new york edition with the headline: obama calls for unity, but signature acts remain in jeopardy. order reprints | today's paper | subscribe
obama calls for unity, but signature acts remain in jeopardy
mark landler julie hirschfeld davis