WASHINGTON — Since the death of Justice Antonin Scalia last February, the Supreme Court has been evenly divided between Democratic appointees and Republican ones. This has resulted in occasional deadlocks and many narrow decisions.

A new justice appointed by President Trump would revitalize the court’s conservative bloc. The balance of power would then return to the one in place since 2006: leaning right, but tempered by the occasional liberal votes of Justice Anthony M. Kennedy.

Mr. Trump said in a Twitter post on Monday that he would announce his pick on Tuesday at 8 p.m.

Here is a look at how a court with a reinvigorated conservative wing might act.

Abortion Rights Appear Secure, for Now

So long as Justice Kennedy continues to support the broad outlines of the constitutional right to abortion established in 1973 in Roe v. Wade, the addition of a new justice is not likely to make a difference.