WASHINGTON, D.C. — As JD Vance transitions from Ohio to Washington, D.C., he is also settling into his job as vice president—a historically vague role.

“The Constitution gives the vice president two functions to preside over the Senate and break tie votes, and to be first in line of presidential succession. But modern vice presidents spend relatively little time in either function,” said Joel Goldstein, law professor emeritus and vice presidential scholar at Saint Louis University.

Modern vice presidents have largely served as advisers to presidents, sometimes offering frank advice in private.

“Beginning with Walter Mondale, vice presidents of both parties have served as close presidential advisers and have been troubleshooters,” Goldstein said.

Publicly, though, vice presidents usually promote the president and his policies. That could prove especially salient for Vance, as President Donald Trump has long valued loyalty,

“The challenge for Vice President Vance is to maintain a favorable relationship with President Trump and to be perceived as helping him solve problems, not create problems,” said Goldstein.

Some vice presidents have been given specific issues to focus on. Former Vice President Kamala Harris was charged with leading diplomatic efforts with Mexico, Guatemala, El Salvador and Honduras to stem migration to the U.S.

For now, Vance has not taken up a specific issue.

As a one-term vice president, Vance is uniquely positioned to run for president himself when Trump’s second term ends.

“It’s a four-year clock, not an eight-year clock,” said Goldstein. “And that puts him in a bit of a different position than virtually all other incoming vice presidents.”

Vance is already getting dispatched to represent Trump’s position on major issues. He is scheduled to speak Friday in Washington, D.C. at the March for Life, an annual rally by abortion opponents.