President Trump and Vice President  Pence meet with Senate Minority Leader Charles E. Schumer (D-N.Y.) and House Minority Leader Nancy Pelosi (D-Calif.) at the White House in December. (Evan Vucci/AP)

Mike Pence has lasted almost two years as Donald Trump’s vice president. That’s an accomplishment of sorts, given the short tenure of many high-level Trump officials. But it’s not clear what Pence has added — or what the next two years will bring for Pence or the office he holds. Let’s take a look at his vice presidency to date — and the difficulties he has faced.

Pence has stepped into the “White House vice presidency” — at least in part

Pence entered an office that had been transformed during the past four decades. For six administrations, presidents followed and entrenched the partnership model that Jimmy Carter and Walter Mondale created. This “White House vice presidency” presented the vice president as a close presidential adviser who assumed important high-level assignments. This model enhanced U.S. government; the president could get candid advice from a senior political official who didn’t have a departmental bias, as well as a high-level official to help handle domestic and international challenges.

Trump and Pence have differences in temperament and background. Nevertheless, some observers expected Pence to be an important, even historic, White House partner, especially as Trump entered office without experience in public service.

Pence has apparently kept some basic resources of the White House vice presidency and taken on legislative, diplomatic and political assignments for Trump. What’s more, his comparative longevity in Trump’s administration gives him a behind-the-scenes familiarity that Trump may value in a thinned White House with few able people interested in coming on board. Trump tried to name Nick Ayers, Pence’s top vice presidential aide, as his own chief of staff, an attempt that suggested an integration of the two operations. (Ayers said no.) And Trump has indicated that he wants Pence as his running mate in 2020. Pence is popular with Trump’s base of religious conservatives and would be a helpful surrogate if Trump faces a primary challenge.

But Pence’s position doesn’t look good

The Constitution, of course, gives Pence a four-year term. And presidents have good reasons not to dump their vice presidents; doing so is likely to upset the base, raise questions about his loyalty and appear weak.

But Trump has been less constrained by conventions than his predecessors; he demands loyalty but rarely extends it. Pence has apparently remained in Trump’s good graces by subjecting himself to a series of indignities. Search for “Pence” and “sycophancy,” and you’ll find a host of articles that document Pence’s obsequious behavior. For instance, in December, when Trump met with Democratic congressional leaders to talk about averting a governmental shutdown, Pence was in the room — and was widely mocked for saying nothing. Of course, what could Pence say as Trump boasted that he would proudly shut down the government, while Senate Minority Leader Charles E. Schumer and speaker-to-be Nancy Pelosi pushed back? Still, it looked bad. Previous presidents negotiated in private; as a result, during the government shutdown in 1995-1996, Bill Clinton’s vice president, Al Gore, was able to participate aggressively in talks with Speaker Newt Gingrich and Senate Majority Leader Bob Dole.

Trump has slighted Pence in other ways. For instance, Pence apparently assured Senate Republicans that Trump would sign a continuing resolution without funding for a border wall. But after the Senate passed the resolution, relying on those assurances, Trump changed his mind. Pence later suggested that $2.5 billion for border security — with no wall funding — would do the trick; Trump repudiated that, as well. (Editor’s note: After publication, the Pence’s office contacted the Washington Post to dispute this characterization. Alyssa Farah, the Vice-President’s Press Secretary, said “The report is incorrect. The offer the Vice President gave to Senator Schumer and others, on behalf of the President, funded the wall.”)  Trump dispatched Pence to preside over a weekend meeting with legislative staffers on the government shutdown, an assignment demeaning to the vice president, especially since Trump trashed the session.

That’s just a taste of how Trump has embarrassed Pence over the past two years. In 2017, Pence echoed the White House’s agreed-upon line that Trump had fired FBI director James B. Comey based on a Justice Department memo — but then Trump told NBC’s Lester Holt that he dismissed Comey because of the Russia investigation. And after Pence made a show of walking out of a football game to protest some players’ kneeling during the national anthem, Trump announced that he had asked Pence to do so.

Until recently, many officials have preferred to deal with Pence rather than with the unconventional Trump. Previous vice presidents had credibility with legislative and foreign leaders because they could speak for and to the president. That might be ending, now that Pence has been publicly proved an unreliable go-between. Pence hasn’t been as effective an emissary to Capitol Hill as were Mondale, George H.W. Bush, Dan Quayle and especially Joe Biden — in part because Pence hasn’t had the strong across-the-aisle relationships they had built. But Biden and the others could reach agreements because they worked with presidents who understood the need to compromise and to protect the vice president’s clout. Pence does not.

Pence, like many of his predecessors, may still be dispatched to Capitol Hill to gather information from Senate Republicans, as happened after they were outraged by Trump’s abrupt decision to withdraw from Syria. But serving as a vent is a thankless, debilitating task — especially if there’s no place to channel the air.

There’s little evidence that Pence offers Trump contrarian advice on policy, as vice presidents Mondale, Bush, Quayle, Gore, Richard B. Cheney and Biden sometimes did with their presidents. They were willing to challenge their bosses, which Mondale conceived as a virtue of the office. If Pence has pushed Trump to find a way out of the shutdown impasse, there is no evidence that he has been heard.

The vice presidency has placed Pence an impeachment away from the presidency and raised his own profile as a presidential candidate. But it’s also associated him, more than anyone else, with the baggage of the Trump presidency.

For now, Trump has said he wants Pence to remain in 2020. Perhaps he will. But Trump’s rejection of presidential conventions and his tendency to sour on close associates make Pence’s vice presidency look iffy. Even if Trump keeps him on the 2020 ticket, his vice presidency remains more challenging — and less meaningful — than those of recent vice presidents because of the president he serves.

Joel K. Goldstein, the Vincent C. Immel Professor of Law at Saint Louis University School of Law, is the author of “The White House Vice Presidency: The Path to Significance, Mondale to Biden” (University Press of Kansas, 2016).