Discarding Donald Trump was the easy part. Breaking ranks with her beloved and beleaguered Republican Party, not so much.

“Some will say that as a Republican I have an obligation to support my party’s nominee,” Sen. Susan Collins wrote in a widely acclaimed op-ed for The Washington Post on Monday. “I have thought long and hard about that, for being a Republican is part of what defines me as a person.”

Meaning the decision by Maine’s senior senator to denounce The Donald, simple as it may have seemed, was in fact complicated. Not because of the clown prince atop the Republican ticket, but rather because of the party that Collins cherishes for its past even as it careens toward an anything-but-certain future.

“I revere the history of my party, most particularly the value it has always placed on the worth and dignity of the individual,” Collins wrote. “It is because of Mr. Trump’s inability and unwillingness to honor that legacy that I am unable to support his candidacy.”

Good for her.

Sure, it took awhile. And yes, Collins happens to be dumping Trump amid his post-convention nosedive in the polls.

Still, to do what Collins did three months before Election Day demonstrates far more courage than the vast majority of her tongue-tied Republican colleagues on Capitol Hill. (We’re looking at you, Rep. Bruce Poliquin.)

Some already have likened Collins’ words this week to the legendary Sen. Margaret Chase Smith’s famous “Declaration of Conscience” repudiation of the red-baiting Sen. Joseph McCarthy back in 1950.

Perhaps. Although in this case, a better banner might be “Only the Lonely.”

Left unsaid in Collins’ Trump disavowal was the glaring reality that Trump did not plant himself atop the Republican ticket. Republican voters, however one might define them these days, put him there. With an exclamation point.

Those same Republican loyalists, many attracted in recent years by social and economic dog whistles that put short-term electoral harvests ahead of long-term grassroots cultivation, no longer look so kindly on the likes of Collins.

A moderate woman (strike one) from the Northeast (strike two) who can’t stand Donald Trump and (strike three) isn’t afraid to say it?

It’s a testament to her political prowess that Collins still has a spot on the Republican roster.

Consider: Last Thursday, Republican voters in Tennessee held a primary to nominate a replacement for outgoing U.S. Rep. Stephen Lee Fincher.

The ballot in the deeply conservative district was jampacked with 13 Republican candidates. Not one of them – I repeat, not one – was a woman.

Consider: According to a recent story in Politico, of the 308 Republican congressional districts that have held primaries this year, only 26 have nominated women.

That’s 8 percent female representation, almost mirroring the 9 percent (down from 11 percent in 2006) in the current House Republican Conference. Meanwhile, women represent 33 percent of the House Democratic Caucus.

Consider: A 2015 report by the Pew Research Center showed that Americans who self-identify as Democrats hold an 80-11 percent advantage over Republicans among blacks, a 65-23 percent advantage among Asian Americans and a 56-26 percent advantage among Hispanics.

Republicans, on the other hand, hold a 49-40 percent advantage among whites, including a 54-33 percent lead among white men who have not completed college.

In short, as the country grows more diverse, so does the Democratic Party. The Republican Party, meanwhile, stagnates.

Collins can at least find consolation in the fact that here in Maine, she’s as popular as ever. But therein lurks an irony: Her success flows not from her party, but from the entire spectrum of Maine’s electorate.

In a recent Maine Sunday Telegram poll of more than 600 Maine voters conducted by the University of New Hampshire Survey Center, a whopping 73 percent said they had a favorable view of Collins.

Break down a number like that and you’d typically see it skew higher with a politician’s own party, start to erode with unenrolled voters and plummet within the opposition party.

Not so with Collins.

Among those identifying as Republicans, 74 percent had a favorable impression of Collins, while 14 percent viewed her unfavorably.

Democrats, at 71 favorable and 14 percent unfavorable, voiced an almost identical opinion.

Independents held Collins in even higher regard, with 77 percent favorable and only 8 percent unfavorable.

Talk about a double life.

Here in Maine, Collins will be a U.S. senator essentially for as long as she wants to be. The fact that she’s a lifelong Republican is overshadowed by the bigger fact that Mainers of every stripe like who she is, what she does and how she goes about doing it.

Yet out there in the Republican hinterlands, has she become an endangered species?

She stands almost alone among mostly white men who inexplicably cower before the likes of Donald Trump, unable to endorse him yet terrified of invoking the wrath of his Twitter thumb.

Collins, with her 832-word takedown of Trump, suddenly makes them all look so small.

You want paralysis? The day after Collins, Maine’s highest-ranking Republican, stood tall against the man who would hijack her party, Maine Republican Party Chairman Rick Bennett put out a statement that tiptoed around any mention of Collins or Trump.

“We are blessed with a broad, open-minded party representing myriad views on specific issues and candidates,” Bennett said. “I have always encouraged our activists to work hard for those Republican candidates they support, and not work against those they don’t support. This is the best way to give our party the definition desired.”

Donald Trump represents the “definition desired” by today’s Maine Republican Party? Did that conclusion come with one of those semicolon winks attached?

Reached by telephone late Tuesday after a day filled with media interviews (she insists she never thought she’d create such a stir), Collins confirmed that no, this was by no means easy.

“Five generations of my family have served in public office as Republicans,” she said. “This is part of my DNA.”

But the woman who proudly organized the Senate’s tripartisan Common Sense Coalition (Maine independent Sen. Angus King also is a member) brushed away the notion that when the smoke shrouding the Republican Party clears after Nov. 8, she’ll be on the outside looking in.

“I’m hard to count out,” said Collins. “If nothing else, I am very persistent. I just don’t give up.”

Monday evening, moments before The Washington Post posted her op-ed online, Collins placed a call to Republican National Committee Chairman Reince Priebus. He didn’t answer.

“So I left him a voicemail telling him what I was going to do because I didn’t want him to read about it,” Collins said. “I was just trying to be courteous.”

And?

“He called back with an incredibly nice message,” Collins said. “It was really a lovely message.”

He probably envies her.