Obamacare:

Replacing and repealing Obamacare, former President Barack Obama's signature health care reform officially called the Affordable Care Act, was a top campaign issue for Donald Trump. As important, however, is the fact that the issue has been rallying cry for Republicans long before Trump took to the political stage. Both taken together are a fairly solid indicator that Obamacare in its current form will likely be repealed and replaced by Republicans in Congress. That Donald Trump signed an executive order pertaining to Obamacare on Inauguration Day only underlines the importance of this issue to his administration, even if the order itself, as experts have argued, was rather vague and without any clear impact.

While it thus seems highly likely that the Republican-controlled Congress will do away with Obamacare, the entire process could take some time. "They maybe able to come with a legislative package in the first 100 days, but it may take longer than that to figure out a way to do it”, said Linda Fowler, a professor of government at Dartmouth University. "There is a reason why healthcare is on the American policy agenda since Harry Truman.”

What's more, Republicans have to tread carefully on repealing a program that has extended health insurance to 20 million Americans and, that despite its many problems, includes elements that are so popular that even Republican governors have urged their colleagues in Washington to keep them. Still, said Christopher Devine, a scholar on the US presidency at the University of Dayton, Trump and the Republicans getting rid of Obamacare "is an issue you can put money on.”

Border wall/Immigration:

Like Obamacare, building a wall along the US-Mexican border had been a key issue for candidate Trump ever since he come down the escalator to declare his candidacy two years ago at Trump Tower in New York. Trump's rapid rise that had him capture not only the Republican nomination, but ultimately the presidency was certainly helped by his constantly repeated promise to not just build a "beautiful wall”, but have Mexico pay for it. That, however, is unlikely to happen.

"I think it is pretty clear at this point that there is not going to be a wall – at least not a physical wall across the entirety of the US-Mexican border”, said Devine. More likely is an increase in border security and surveillance efforts, for instance through drones.

During the campaign Trump had also promised a much tougher stance on immigration. He suggested at one point to ban Muslims from entering the US and to deport all estimated 11 million undocumented immigrants. As the campaign went on Trump softened both proposals. Still, said Devine, "it is very difficult to say what Trump regards as his current policy stance on any of these issues and what he will feel obligated to follow through on.”

But if his combative inauguration address framed around the Trump administration's motto contentious ‘America First' is any indicator than illegal immigrants should brace themselves for tough times.          

"Every decision on trade, on taxes, on immigration, on foreign affairs will be made to benefit American workers and American families”, Trump said in his Inaugural speech. "We must protect our borders from the ravages of other countries making our products, stealing our companies, and destroying our jobs.”

He also vowed: "We will bring back our borders.”

Trade: 

Brandishing existing trade agreements as job killers was a signature issue that enabled Donald Trump to woo workers in traditional rust belt states like Michigan. He promised not only to rescind or renegotiate the North American Free Trade deal NAFA, but also to pull the US out of the Trans-Pacific trade agreement TPP on day one of his administration. While that has not happened yet, trade is likely to remain on the agenda, simply for the fact that it involves two things Donald Trump believes he is an expert on: international business and deal-making.

While it is a legally unresolved question whether the president has the power to pull out of existing treaties like NAFTA without involvement of the Senate, said Dartmouth's Fowler, there are other things he could do to advance the issue. "What he could do is appoint a special trade representative, a treaty negotiator, but this is a president who has filled very few of the offices he was supposed to fill so far”, she added.

"I think he will deal with trade, noted Devine, "but I wonder whether this won't come later and whether he would renegotiate NAFTA in a dramatic way.”

Foreign policy:

Since the launch of his campaign Donald Trump has not just promised to defeat the terrorist group ‘Islamic State' in no uncertain terms. More than that he has repeatedly doubled down on his promise and even expanded it. The strongest, most sweeping and most prominent vow in this regard came in his Inaugural address where he promised to completely eradicate Islamic Terrorism "from the face of the Earth.”

"Good luck with that one”, said Fowler. On a more serious note, she pointed to what she considered a contradiction not just in his ‘America-First'-centric Inauguration speech, but in his foreign policy approach more generally. "You can't both be isolationist and eradicate terrorism from the face of the earth.”   

University of Dayton's Devine said President Trump could certainly take measures to combat Islamic terrorist. But if his promise to completely eliminate Islamic terrorism is taken at face value, than Trump has already set himself up for failure: "These are promises that no president, no country can deliver on, certainly not within a four year period. It is not under Donald Trump's control or even in that of the United States government to fully eradicate radical Islamic terrorism.”