Sen. Susan Collins on Monday became perhaps the most prominent Republican to disavow her party’s nominee for president. On Tuesday, Donald Trump showed why others have an obligation to follow her.

Republicans should reject Trump’s brand of politics, not because his comments – which insinuated that Hillary Clinton should be shot – go too far, but because those comments show there is no limit to how far he will go to awaken the worst impulses in the American electorate.

Whether he wins or loses, that bell cannot be unrung. The only right response is widespread condemnation, and a collective agreement that Trump’s way of doing business has no place in the public arena.

Trump’s comments can no longer sanely be brushed off as “just words,” and not just because that argument forgets the power given to the words of someone in such a prominent position.

And they cannot be explained as media overreaction to mere slips of the tongue.

On Tuesday, Trump implied that gun owners should take matters into their own hands if, as president, Hillary Clinton were to try to lessen Second Amendment protections. Only the most blinkered interpretation could see his comments any other way.

It may have been a joke, but it was a joke about assassinating a president of the United States, delivered to a crowd that often shouts, “Kill her!” when Clinton’s name is mentioned.

Trump’s more sane backers can perhaps brush that off as political hyperbole. But they are not his audience.

They are not his audience when he retweets the words of white supremacists. They aren’t his audience when he says the election is “rigged.”

And they aren’t his audience when he disparages a Mexican American judge, calls for “punishment” for women who get abortions, or hints that President Obama was not born in this country, or that Obama sympathizes with terrorists.

His audience is the significant portion of America that feels cheated out of their place in the country and is looking for an explanation, and a catharsis. They haven’t gotten any redress from within the system, so they are looking for some from without, and Trump, through exaggeration and simplification, outright lies and fear-mongering, is giving it to them.

It is entirely possible that Trump thinks of it as some sort of game where getting applause and angry screams is the goal.

But he won’t have to live with the consequences if he loses. The rest of us will be left to deal with a portion of the electorate that has been led to believe that the system is a scam, and that their last, best hope has been swept aside by unjust forces.

Trump may say he is kidding when he touts violence and vitriol as the only response to the country’s problems, but to a sizable portion of his supporters, it is no joke.

That’s why it is so important for political leaders of all stripes – including U.S. Rep. Bruce Poliquin, R-2nd District, who has avoided commenting on Trump to the point of absurdity – to stand up for decency.

Trump’s candidacy shows that discontent has been bubbling near the surface for some time, and with every disparaging comment – about women, Muslims, Mexicans or whoever’s next – that anger is drawn out, justified and normalized.

Of course, he keeps those comments just ambiguous enough that he can deny their true meaning. That provides cover to those who keep supporting him out of loyalty to party, or some dream that the conservative policies a Trump presidency would advance are worth having Trump as president.

But after this long, it is clear exactly what he is doing, and we’d be foolish to think otherwise. Forget the presidency – Trump is not fit for the platform of a major-party candidate, and history will speak poorly of those who don’t say so.