Donald Trump is moving aggressively to strengthen his troubled presidency by ousting Reince Priebus as White House chief of staff and replacing him with retired Marine Gen. John Kelly. But the real problem is Trump himself and whether he can restrain his relentless combativeness, limit his impulsive behavior, curb the intimidation tactics that have alienated many potential allies, and allow Kelly to reduce the extraordinary frictions within the West Wing, according to historians, political scientists and strategists for both major parties.

The reshuffle comes at a perilous time for Trump, whose job approval ratings are at historic lows, making him less persuasive than ever on Capitol Hill. Much will depend on whether he realizes how much political trouble he's in. And a big part of his administration's future will be determined by whether Trump gives adequate authority over the staff, policymaking and communication to Kelly, a disciplinarian who has been Trump's secretary of homeland security. Kelly takes over the White House staff Monday.

Last week, Trump failed to persuade the Senate, controlled by fellow Republicans, to pass legislation to repeal and replace former President Barack Obama's health care law. The defeat came even though GOP leaders have been promising to dismantle Obamacare for years, and Trump made ending Obamacare one of his top priorities during the 2016 campaign. On Saturday, Trump said Republicans would look like "fools" if they failed to deliver on overhauling health care. On Sunday, he wrote on Twitter, "Don't give up Republican Senators, the World is watching...Repeal & Replace...and go to 51 votes (nuke option)."

The trouble is that the Republicans couldn't muster even 50 votes on legislation to repeal and replace Obamacare last week and it needed only 50 to pass. The GOP controls the Senate over the Democrats and independents who caucus with the Democrats, 52-48.

Backbiting and infighting in the White House have reached extraordinary levels, and new White House Communications Director Anthony Scaramucci spent much of last week demeaning and attacking Priebus with profanity rarely heard publicly in Washington. The president also has been harshly criticizing his own attorney general, Jeff Sessions, on a variety of grounds, raising questions about whether he will allow Sessions to remain the nation's top law enforcement officer for much longer. And U.S. relations with North Korea, Iran, China and Russia appear to be deteriorating.

In any White House, power flows from the president, and this is of course true in Trump's administration. He believes in creative tension, which he encouraged for many years in his business enterprises. But the result has been backstabbing and infighting that has regularly thrown the White House off message and into disarray. Trump's regular tweets have had the same result. All this has led to a chaotic West Wing that can't get Trump's legislative agenda moving and where aides seem unsure of what the president wants to do and how he wants to do it.

This dynamic has been evident in Trump's shifting statements on what he is seeking in health care reform, in his fluctuating comments about working with foreign allies in military alliances, and, most recently, in his surprise announcement last week that transgender soldiers will no longer be allowed to serve in the military, which took even the Pentagon brass by surprise.

In another sign of reduced influence, Trump is being forced to accept legislation limiting his ability to lift sanctions against Russia. He says privately that the measure goes too far in restricting his authority. But he has apparently decided to go along because it was approved by such an overwhelming margin that a veto would be overridden, according to White House and congressional aides.

And of course there is the investigation by special counsel Robert Mueller, which is causing Trump endless frustration. Mueller is looking into the possibility that Trump aides colluded with Russia last year to undermine the campaign of Democratic presidential nominee Hillary Clinton. Trump calls it a "witch hunt" that is wasting everyone's time and unfairly damaging his credibility.

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If Mueller expands his probe to include Trump's business empire for possible links to Russia, it's likely to cause an escalation of Trump's anger and resentment, and may encourage him to fire Mueller at some point.

"It is very important in any White House to be able to have someone like a chief of staff be able to look the president in the eye and tell him when he's wrong and tell him when he's going to make a mistake," said Leon Panetta former White House chief of staff for President Bill Clinton. Any president needs this kind of "support system," Panetta said, adding in a CNN interview: "The real test is whether he [Kelly] can develop that kind of relationship with Donald Trump." It won't help if Kelly fails to dilute the various power centers in the White House which developed under Priebus, Panetta said.