Grover Cleveland had less than a year as Mayor of Buffalo and two years as Governor of New York.

He was a straight-talking populist who was unwilling to kowtow to the entrenched and corrupt elements of the Democratic status quo. He won an electoral landslide because the country was eager for reform.

Cleveland ran against a Republican who had 5 terms in Congress — three as Speaker of the House, four years in the Senate and a stint as Secretary of State. He was an aggressive politician and a formidable debater. Nevertheless, he lost to the plain-speaking populist newcomer.

I suppose that Cleveland isn't "modern" enough to meet your arbitrary criteria, but there's a story here — a story that could very well repeat this year.