TEHRAN — At his first presidential campaign rally, Saeed Jalili on Friday welcomed the cheers of thousands of young men as he hauled himself onto the stage. His movements were hampered by a prosthetic leg, a badge of honor from his days as a young Revolutionary Guards member in Iran’s great trench war with Iraq.

“Welcome, living martyr, Jalili,” the audience shouted in unison, most of them too young to have witnessed the bloody conflict themselves but deeply immersed in the national veneration of its veterans. Waving flags belonging to “the resistance” — the military cooperation among Iran, Syria, the Lebanese Shiite group Hezbollah and some Palestinian groups — the crowd roared the candidate’s election slogan: “No compromise. No submission. Only Jalili.”

Mr. Jalili, known as Iran’s unyielding nuclear negotiator and a protégé of the supreme leader, Ayatollah Ali Khamenei, is emerging as the presumed front-runner in Iran’s presidential election on June 14, an unsettling prospect for future relations with the West. Mr. Jalili, 47, who many analysts say has long been groomed for a top position in Iran, is by far the most outspoken hard-liner among the eight candidates approved to participate in the election.

Opposing “détente a hundred percent” and promising no compromise “whatsoever” with the West over matters like Iran’s nuclear program and involvement in Syria, Mr. Jalili seems set to further escalate Iran’s standoff with the United States and its allies if elected president.