President Trump in the White House in Washington on Dec. 6. (Jabin Botsford/The Washington Post)

PRESIDENT TRUMP’S decision to recognize Jerusalem as Israel’s capital has a certain amount of common sense on its side. As a practical matter, West Jerusalem has been the seat of Israeli government since 1949, and no conceivable formula for Palestinian statehood would change that. Political leaders and diplomats from around the world already visit government offices there, even if their embassies remain in Tel Aviv. As Mr. Trump put it, for the United States finally to accept that the Jewish state has its capital in Jerusalem is “nothing more or less than a recognition of reality.”

At the same time, Presidents Bill Clinton, George W. Bush and Barack Obama had good reasons for holding back on such a move, even though they, like Mr. Trump, had promised while on the campaign trail to move the U.S. Embassy to Jerusalem. They calculated that what amounted to a mostly symbolic step could undermine U.S. policy across the Middle East as well as their hopes of brokering an Israeli-Palestinian settlement — and possibly trigger violence, including against Americans.

Mr. Trump cast himself as setting aside failed conventional wisdom — he pointed out there has been no peace deal — and of offering a fresh approach. That’s a stance that may play well with his domestic political base and with many Israelis. But Mr. Trump is implicitly betting that previous presidents were wrong to worry about blowback in the Middle East and beyond. That’s a big risk to take for the scoring of political points.

So far, the president’s decision has been rejected by every major U.S. ally in Europe and the Middle East, including Britain, France, Egypt and Saudi Arabia. It will put considerable pressure on Jordan, Israel’s fragile neighbor, whose King Abdullah II sees himself as a protector of Jerusalem’s holy Muslim sites. It will probably make it harder to promote a tacit alliance between Israel and Sunni Arab states against Iran, as Tehran will surely exploit the Jerusalem issue. It will also virtually ensure that Palestinian leaders respond unfavorably to the peace initiative the Trump administration says it is preparing. If violence erupts in Jerusalem or elsewhere in the Middle East — and extremists will do their best to make that happen — Mr. Trump will be blamed.

Mr. Trump made some effort to mitigate such damage. He said his administration was “not taking a position [on] any final status issues, including the specific boundaries of the Israeli sovereignty in Jerusalem,” words that leave room for an eventual settlement in which a Palestinian state would have its capital on Jerusalem’s eastern side. He did not refer to the “united Jerusalem” promoted by Israeli leaders, who aspire to maintain permanent control over neighborhoods where some 300,000 Palestinians live. He called for maintenance of the status quo at the city’s holy sites, including Muslim holy places that are currently controlled by Muslim authorities.

Nevertheless, those caveats had the ring of boilerplate inserted by the president’s advisers. The heart of Mr. Trump’s speech was his boast that “while previous presidents . . . failed to deliver” on their campaign promises about Jerusalem, “I am delivering.” Those who genuinely hope for peace in the Middle East can only hope that this preening display will, as the president predicted, produce positive rather than negative results.