WASHINGTON — President Trump’s Rose Garden speech outlining a major overhaul of the nation’s immigration system was intended to strike a centrist, conciliatory tone on the issue that would appeal to Democrats and make them seem unreasonable for criticizing it.

But within minutes of taking the podium on Thursday, Mr. Trump struck a more familiar tone, bashing Democrats as advocates of “open borders, lower wages and, frankly, lawless chaos” and promoting the importance of constructing a “desperately needed” wall along the southwestern border — a move they have vehemently opposed.

The president also framed the immigration debate in terms of his re-election campaign, threatening that if Democrats refused to support what he called his “merit-based, high-security plan,” he would pass it “immediately after the election, when we take back the House, keep the Senate and, of course, hold the presidency.”

Democrats and immigration advocates have long opposed many of the proposals outlined by Mr. Trump, like scaling back the family-based immigration system, which allows immigrants to bring their spouses and children to live with them, and replacing it with a merit-based system that would provide opportunities for immigrants with valuable job skills and education.