She has long prided herself on never missing a vote in the U.S. Senate. But of all the thousands she’s cast in her 21 years on Capitol Hill, this is the one on which Sen. Susan Collins’ legacy will hinge.

She can vote later this month to confirm Brett Kavanaugh to the U.S. Supreme Court and hope – no, make that pray – that he stands by his assurance to her that Roe. v. Wade is “settled law.” (Whatever that means.)

Or she can open her eyes to what many others already see – that Kavanaugh represents the tipping point in the never-ending battle over a woman’s right to choose an abortion – and vote to keep him off the highest court in the land.

“I know it’s frustrating to the press, but until I finish my review I’m going to defer my decision-making,” Collins told Portland Press Herald reporter Joe Lawlor on Friday as the weeklong hearing on Kavanaugh’s nomination concluded with two questions still unanswered:

Would Kavanaugh, or would he not, provide the crucial fifth vote on the court to overturn Roe. v. Wade, the landmark abortion decision that for 45 years has rightly left to a woman and her physician the decision on whether to proceed with a pregnancy?

Or, short of tossing out Roe. v. Wade in its entirety, would Kavanaugh and the rest of the court’s conservative block embark on a piece-by-piece dismantling of a woman’s right to choose until, as a skeptical Sen. Angus King put it Friday, all that’s left of the historic ruling is “a hollow shell”?

Clearly, as Senate Republicans scramble to vote Kavanaugh in before the Supreme Court begins its next session on Oct. 1, Collins appears to be leaning toward confirmation.

After a closed-door sit-down with the nominee last month, she emerged to say that Kavanaugh assured her that Roe v. Wade is “settled law.” On Friday, she followed that up by noting that Kavanaugh “often describes Roe as precedent upon precedent.”

None of which, when it’s all said and done, comes close to satisfying the one marker that Collins laid down back when Justice Anthony Kennedy announced his retirement in June: Kennedy’s successor, as Collins put it, must not be “hostile” to Roe. v. Wade.

Last month, I asked Annie Clark, Collins’ spokeswoman, how the senator might define such “hostility.”

Clark replied in an email: “An example of a time when Senator Collins determined that a judge was hostile to Roe was when she voted against Judge William Prior, a George Bush nominee who called Roe ‘the worst abomination of constitutional law in our history.’ ”

Talk about a low bar. A judicial nominee must be dumb enough to bombard the Supreme Court with rhetorical fireworks before Collins will turn thumbs down on his or her nomination.

Brett Kavanaugh, if he taught us one thing during his often-rocky hearing last week, is not that dumb.

Rather, he hemmed and hawed and, when the going got really tough, simply rebuffed any and all attempts to discern where he stands on abortion and other critical issues of our time.

Thus, we are left to consider what did leak out: The now infamous 2003 email in which Kavanaugh, at the time working for the George W. Bush administration, opined: “I am not sure that all legal scholars refer to Roe as the settled law of the land at the Supreme Court level since Court can always overrule its precedent, and three current Justices on the Court would do so.”

Collins was quick to point out that Kavanaugh meant other “legal scholars,” not himself. Perhaps, but if I were Maine’s senior senator, Kavanaugh’s quickness to acknowledge that school of thought would at least give me pause.

In a similar vein, Kavanaugh in his testimony Thursday referred to contraceptives as “abortion-inducing drugs” while describing a case involving insurance coverage for all forms of birth control.

Let’s dispense with the fact that such hot-button language, a staple of the anti-abortion movement, is scientifically wrong – as a multitude of scientific and medical experts later noted on Twitter.

More significantly, the phrase offered a fleeting glimpse into the thinking of a man hellbent on not letting the world see inside his head – or, for that matter, his heart – when it comes to a woman’s right to control her own body.

“Saying ‘abortion-inducing drugs’ to describe contraception is straight out of the anti-choice, anti-science phrase book used to restrict women’s access to essential health care,” noted the Center for Reproductive Rights on Twitter.

The problem with Collins, as she inches her way toward what looks like a vote to confirm Kavanaugh, is that she’s trying to have it both ways.

She holds firm to her pro-choice reputation by vowing that she will oppose any nominee “hostile” to Roe v. Wade. But when it comes to rooting out such hostility, she appears more than willing to take Kavanaugh at his word and steer clear of what may lie hidden among the weeds.

Put more simply, she seems far too trusting of what Kavanaugh told her – echoing last winter’s debacle when she voted for massive high-end tax cuts in exchange for Senate Majority Leader Mitch McConnell’s promised protections of the beleaguered Affordable Care Act. After the tax bill passed, the promises went poof.

Some argue that Collins’ naiveté last winter was a ruse – that she knew all along she’d be shortchanged by McConnell, yet forged ahead on the assumption that voters would forget all about it before she has to face them again in 2020.

Maybe so. But as she now prepares to vote yea or nay on Kavanaugh, Collins would do well to take a long, hard look at the political landscape.

More than a dozen cases involving abortion currently are queued up at the Supreme Court’s doorstep – any one of which could spell the beginning of the end for Roe. v. Wade.

Kavanaugh, if confirmed, will all but certainly side with the court’s other conservatives in those cases – dealing one or more blows to Roe v. Wade if not dismantling it altogether.

And, with all of that playing out under the shadow of the looming 2020 election, Mainers long comfortable with Collins and her pro-choice persona will find themselves in a decidedly different mood when it comes to her political future.

The word “hostile” comes to mind.