Trump's tough line on Iran put to the test in election year

President Trump has successfully hardened U.S. policy toward Iran since pulling out of the Obama-era nuclear deal 17 months ago, engineering a dramatic shift in policy that has rankled America’s allies in Europe but won deep praise from Israel and several key Arab powers.

But that policy is likely to be strongly tested this year, national security insiders say, with the world watching warily to see whether the administration’s “maximum pressure” approach manages to contain Tehran or triggers a dangerous escalation as Mr. Trump heads into his fourth year in...