U.S. President Donald Trump's success in scoring a second-term in the Oval Office in 2020 will depend on how much his domestic and foreign policies work, according to former White House official Anthony Scaramucci. Speaking to CNBC's "Capital Connection" on Tuesday, Scaramucci said Trump will be "very tough to beat" if three things work out: The U.S. economy continues to grow, the president's border security strategy excites his political base, and his foreign policies yield results. "If those things happen and the economy continues to grow, I think he'll be very tough to beat in 2020," said Scaramucci, the founder and co-managing partner of investment firm SkyBridge Capital.

US economy

He predicted that a thriving U.S. economy will boost Trump's chances of getting re-elected to around 85 percent. If growth slows down — as forecast by many economists — Trump still has a 60-percent to 65-percent chance of winning the election, Scaramucci added. The International Monetary Fund said in January that the U.S. — the world's largest economy — is expected to grow at 2 percent this year, down from the estimated 2.3 percent for last year. That growth could slow down further to 1.8 percent in 2020, according to the IMF.

President Donald Trump speaks during a rally at Florida International University on February 18, 2019 in Miami, Florida. Joe Raedle | Getty Images

Equity markets

But economic growth is not the only thing that's important for Trump, the performance of the U.S. stock market matters too, said Scaramucci, who had a short stint as Trump's communications director. "I like to tell my friends that the only poll the president's really concerned about is the . He looks at that pretty much daily and if it's going in the right direction, he thinks his re-election chances are pretty great," said the former White House official. The president is also "very, very concerned" about border security because he thinks it plays very well to his base, according to Scaramucci. Disagreements on border security — specifically, on the U.S.-Mexico border wall that Trump proposed — led to the longest partial government shutdown in American history. It remains an area of contention between the Republican president and Democratic members of Congress, with Trump declaring a national emergency as a way to get funding to build the wall.

Foreign policies