One year almost to the day from the murder of nine black churchgoers in Charleston, Barack Obama flew to the scene of another massacre. He had an unlikely political ally in tow.  Related: How the Orlando shooting unfolded: 'He came in with the intent of evil'  Marco Rubio officially joined the president and vice-president on Air Force One on Thursday, in his capacity as a Florida senator – demonstrating national unity in one of the bleakest weeks in US history.  Where the Charleston killings stirred bitter memories of racial violence, the murder of 49 people and wounding of 53 at an LGBT nightclub in Orlando represented America’s deadliest mass shooting, one the world’s worst homophobic atrocities and a seeming recurrence of jihadi-inspired domestic terrorism all in one sickening blur.  At first the political response appeared only to add to the heartache. Within hours of last Sunday’s attack by Omar Mateen – a 29-year-old Muslim American whose father emigrated from Afghanistan – Donald Trump delivered an anti-immigration speech that was shocking, even by his standards, for its apparent suggestion that Obama was to blame. When the Washington Post reported his subsequent insinuation that the president harboured a secret agenda somehow linked to the attack, he banned the newspaper from covering his campaign.  But just as some in Europe are now hoping that the assassination of the British MP Jo Cox could mark a turning point in the anti-immigration mood surrounding Britain’s referendum on EU membership, Trump’s response to Orlando looks as if it may mark a high water point in the nationalist tide that has engulfed the US presidential election.  Coming swiftly after his criticism of a judge’s Mexican heritage, Trump’s apparent blanket attack on Muslim Americans was too much for many Republicans in Congress.  Senate majority leader Mitch McConnell said he “was not going to be commenting on presidential candidates”, even though campaigning is now in full swing. Bob Corker, another elder statesman recently seen as Trump’s most likely running mate, said he was “discouraged” by the words of his party’s presumptive nominee.  In this context, Rubio’s appearance aboard Air Force One alongside Obama and Joe Biden was more than just a Florida courtesy. Something had snapped.  This was the same Senator Rubio who, as a Republican presidential candidate, had spent much of the year attacking Obama as unfit to lead. This was perhaps the fiercest critic of White House foreign policy throughout the 2016 campaign, coming to the scene of an Islamic State-inspired terrorist attack and making clear he stood with the president, not his party’s likely nominee.  This weekend, rumours are swirling again in Washington of one final bid to deprive Trump of his place as the Republican nominee when the party convention meets in Cleveland next month.  Late on Friday Sean Spicer, communications director of the Republican National Committee, was forced to remind plotters that Trump has “bested 16 highly qualified candidates and received more primary votes than any candidate in Republican history”.  Related: Obama at Yosemite attacks 'lip service' to natural beauty amid climate inaction  “All of the discussion of the RNC rules committee acting to undermine the presumptive nominee is silly,” he insisted.  Yet many Republicans fear not just the prospect of losing the White House in a landslide this November, but also ceding control of the Senate and House of Representatives. If Trump is at the top of the ballot, their party’s brand could be tarnished for a generation. Democrats are compiling a growing list of GOP figures willing to back their nemesis, Hillary Clinton, rather than contemplate Trump any longer.  It is not just disarray in the Republican party that is bringing Washington’s political establishment slowly back together. Obama himself is undergoing a renaissance in popularity, hitting his highest approval ratings since 2012 just as Trump hits new record lows.  At the last midterm elections, in 2014, not even Democratic senators would be seen with Obama, such was his reputation for repelling moderate voters. The Senate was lost. But now, even the most hawkish of Republicans would rather be seen with the president than the titular head of their own party.  Images of Rubio and the Obama shaking hands on the tarmac were all the more surprising amid rumours – confirmed this weekend – that the Florida senator was about to change his mind about not standing for re-election this November.  “No hug. No hug. I might run again,” ran a spoof caption on a viral video of the two appearing to come close to an actual embrace – something that once nearly sank the career prospects of New Jersey governor Chris Christie, after hurricane Sandy.  Not all Republicans are ready to embrace the president’s foreign policy. The veteran Arizona senator John McCain, a moderate with hawkish national security credentials, appeared briefly to come to Trump’s rescue on Thursday, telling reporters he also believed Obama was “directly to blame” for Orlando. He later retracted the remark, but only partly.  Even Obama’s own administration is far from unified on the vexed question of how to handle Isis. It emerged this week that 51 diplomats had signed a memo, via an internal “dissent” procedure at the State Department, that was sharply critical of the president’s policy on Syria.  Nonetheless, what began as a terrible week for America, looked like ending as a good one for its president. Although the Orlando massacre forced Obama to postpone the first of many planned rallies in support of Hillary Clinton as the presumptive Democratic nominee, her opponent was already working hard to make him look more popular than he has in a very long while.  Obama is fast becoming the ace up Clinton’s sleeve, a figure who, by comparison with Trump at least, now appears a unifier.  Clinton and Obama’s postponed trip to Green Bay on Wednesday points to the president’s likely role over the coming months. He won Wisconsin handily in 2008 and 2012, but the state is typical of the blue-collar union battlegrounds in which Trump hopes to rewrite the electoral map.  Not since 1988, when Ronald Reagan headlined some 20 rallies to help his vice-president, George HW Bush, has an incumbent planned such an active role in the election of his successor. Even then, the Gipper’s alleged Alzheimer’s appears with hindsight to have been a limiting factor.  Bill Clinton and George W Bush were not seen by Al Gore and John McCain as key electoral assets, due to the problems they faced toward the end of their administrations: chiefly Clinton’s impeachment and Bush’s Iraq war legacy.  Related: Legal experts on Donald Trump: 'He lacks respect for basic norms'  Republicans long assumed that they could hurt Hillary Clinton by linking her to the divisive aspects of the current White House: foreign policy, Obamacare, immigration and gun control. Against a more orthodox Republican opponent, these might still have been liabilities, particularly in swing states where socially conservative voters are important.  Now, Clinton’s decision during the primary to embrace this characterisation of her as an extension of Obama’s third term is likely to continue into the general election, especially now that she is running against an opponent who, like Bernie Sanders, will target her in the relatively liberal rustbelt.  In more diverse swing states like Florida, Trump’s divisive rhetoric on race also increases the benefits of having Obama onboard. In the sunshine state, with its large Hispanic vote, even a Republican senate candidate such as Rubio is more likely to benefit from having the president on his arm than by getting too close to the Donald.  For Clinton, there could hardly be a better reminder of her credentials as a grown-up – and a more experienced commander-in-chief – than her old boss.
GOP nominee’s Orlando response sees Republicans desert him in droves while president set to be widely deployed in campaign for Democratic successor