Donald Trump famously won the combined 56 electoral votes of Pennsylvania, Wisconsin, and Michigan by a total of 77,744 in the popular vote. Had those quarter-percentage-point squeakers gone the other way in the three states, Hillary Clinton would have won the Electoral College in addition to the popular vote, by a score of 283 to 248. It's no wonder that the president's re-election campaign is focused foremost on, well, Pennsylvania, Wisconsin, and Michigan.

Enter fifth-term Michigan congressman Justin Amash (R-Grand Rapids). The self-described libertarian Republican has been openly weighing a presidential challenge under the banner of the Libertarian Party (which selects its nominee in May 2020), so his home-state media is starting to assess the potential impacts of such a run. Some initial headlines: "Amash could play 2020 spoiler in Michigan as Libertarian nominee," and "Amash's presidential decision could spell trouble for Trump in Michigan."

Here's how the math works. Trump won Michigan (and its 16 electors) by a margin of just 10,704 votes, or 47.5 percent to 47.27 percent, becoming the first Republican to win the Great Lakes State since George H.W. Bush in 1988. Libertarian nominee Gary Johnson in 2016 received 172,136 votes, or 3.59 percent. Amash in that same election won 203,545 votes in his district alone. (A district in which Amash's 22-point victory was considerably more impressive than Trump's 9.4-point edge over Clinton.)

"Tens of thousands of people in West Michigan have voted for Justin Amash. They don't just walk away from him suddenly," Lansing-based pollster Richard Czuba told the Detroit News. "That's not to say he'd get the same number of votes by any stretch, but it wouldn't take a lot of votes to siphon away if Michigan were a close race."

Bernie Porn, of the Lansing-based political polling firm EPIC-MRA, told Michigan Advance that "He could have a heck of a lot bigger impact on the outcome than Johnson in 2016."

Early polling has the president facing an uphill re-election slog in the Rust Belt. In a Michigan survey released a month ago, Emerson Polling had Trump losing in all five head-to-head matchups with selected Democrats, by between two and eight percentage points, including an additional two contests that threw in independent Howard Schultz (who, interestingly, has been pulling about equally from major-party candidates).

Amash told the Detroit News that he rejects the single-state spoiler frame.

"Who knows? Maybe he'd deny me Michigan. I don't know," the congressman said. "That kind of perception of third-party candidates and independent candidates is a problem….One of the reasons it's persisted as a problem is we haven't had strong candidates typically running third-party campaigns or independent campaigns. I really think if you have a strong candidate, that person can far exceed expectations."

If Amash decides to run, he'd have to give up his congressional seat—Michigan law forbids federal candidates to run for two different positions in the same election. Then again, his whole district might be redistricted out of existence after a 2020 Census that's expected to reduce the state's congressional delegation by one seat.

So will he run? Amash told the News that "'Considering' is too strong a word" to describe his deliberations, and also that "you also only run for things if you feel like there's a good possibility of winning." As for the comparatively marginal status of the party's ideology: "If you can get people to think about libertarianism as the philosophy of America — that it is just an appreciation for American principles of individualism and liberty and freedom — I think it's very accessible to a lot of people."