In the short term, when he fills the seat left vacant by the late Justice Antonin Scalia, he will likely return the court to the status quo before Scalia's death.
But with three justices in their late 70's and early 80's -- it's the next seat or seats that could make the difference.
"I have said that I will hold this office as long as I can do the job full steam," the 83-year-old Ruth Bader Ginsburg told PBS' Charlie Rose in September. "I know that this year I'm OK. At my age you have to take it year by year."
Adding two new conservative appointees to the court could lead to restrictions on abortion a further loosening of campaign finance rules, the lifting of gun restrictions, the limiting of environmental rules, and a further emphasis on the power of states over the federal government.
"Here's the story," Trump said on the campaign trail in Cedar Rapids in July. "If you really like Donald Trump -- that's great -- but if you don't you have to vote for me anyway -- you know why? Supreme Court judges! Supreme Court judges!"
And although plenty of Republicans questioned Trump's policies, judicial conservatives are thrilled with the list of 21 potential nominees he put forward. Their only worry is to make sure he would keep his word. He worked hard to soothe them on the campaign trail, but is not bound by the list.
"The real question to which we may now find out the answer is just how serious Mr. Trump was about replacing Justice Scalia with a judge cut from the same cloth, and how much pressure he'll receive from Republicans in the Senate to stick to his original list -- or a judge with similarly conservative credentials," said Steve Vladeck, CNN contributor and professor of law at the University of Texas School of Law.
"President Bush tried to go outside the box when he nominated his White House Counsel, Harriett Miers, to replace Justice O'Connor -- but ended up having to withdraw her after facing conservative blowback," Vladeck added.
It was in May that Trump unexpectedly released a list of 11 judges.
The list included: Steven Colloton of Iowa, Allison Eid of Colorado, Raymond Gruender of Missouri, Thomas Hardiman of Pennsylvania, Raymond Kethledge of Michigan, Joan Larsen of Michigan, Thomas Lee of Utah, William Pryor of Alabama, David Stras of Minnesota, Diane Sykes of Wisconsin and Don Willett of Texas.
Pryor, of the US Court of Appeals for the 11th Circuit, has described Roe v. Wade as "the worst abomination in the history of constitutional law."
At his confirmation hearings in 2003
Sen. Chuck Schumer brought up the issue of abortion.
"Now, you have said on occasion, on several occasions, that Roe v. Wade is quote, 'the worst abomination in the history of constitutional law.' Do you believe that as of right now? "
Pryor responded: "I do."
Sykes wrote an opinion in favor of business owners and closely held corporations asserting a religious objection to the so-called Obamacare contraceptive mandate.
Second list of Trump judges
In September, Trump had added to his list, perhaps in response to critics who noted the first list was made up of mostly white men.
US District Court Judge Amul Thapar was the first South Asian to be named to an Article III federal judgeship in 2007.
US District Court Judge Federico Moreno serves on the district court for the southern district of Florida, is Hispanic and was born in Venezuela.
Robert Young, the Michigan Supreme Court's chief justice, is African-American.
Judge Margaret Ryan is a military veteran and serves as a judge on the US Court of Appeals for the Armed forces.
The only non-judge on the list was Sen. Mike Lee of Utah -- coincidentally a close friend of Trump's former presidential primary rival Sen. Ted Cruz. While Lee declined to back Trump, Cruz endorsed the GOP nominee later in the day the list was released.
Diversity is something Scalia indirectly advocated for in an opinion in the same-sex marriage case.
While questioning why judges should be in the position to decide the case instead of the people, Scalia noted that the court "consists of only nine men and women, all of them successful lawyers who studied at Harvard or Yale Law School. Four of the nine are natives of New York City. Eight of them grew up in east-and west-coast States. Only one hails from the vast expanse in between. Not a single Southwesterner or even, to tell the truth a genuine Westerner (California does not count)."