“Scott seems, like Ronald Reagan, to have a ‘happy warrior’ aspect about him and to relish, with a smile, spirited combat, as he did in those battles with the public-employee unions,” said Patrick J. Buchanan, the conservative commentator, who worked in the Reagan White House. “Also, there seems about Walker — and I do not say this pejoratively — a simplicity, an absence of calculation and deviousness, that is attractive to voters looking for someone fresh and honest to believe in.”

But by inviting such comparisons, Mr. Walker also risks overreach.

In January, he said that “documents released from the Soviet Union” had proved that its leaders took Reagan more seriously as a result of his firing of the air traffic controllers. But the Soviet “documents” apparently did not exist. (Mr. Walker later said he was referring to articles he had read.)

In February, he called Reagan’s firing of the controllers “the most significant foreign policy decision in my lifetime” because it showed the Soviet Union Reagan’s resolve. During Mr. Walker’s lifetime, however, the nation has seen its share of war and peace, international crises, and the opening of China.

He also drew fire when, asked how he would handle the Islamic State as president, he said, “If I can take on 100,000 protesters, I can do the same across the world.”