She has a decision to make. And with history’s fault lines spreading out beneath her feet, Sen. Susan Collins best make it sooner rather than later:

Should Maine’s senior senator, already no friend to President Trump, join the call for a special prosecutor to investigate Russian involvement in last fall’s election, now that Trump has abruptly given James Comey the heave-ho as FBI director?

Or should Collins stand fast with her fellow Senate Republicans and insist that Comey’s firing on Tuesday – only the second in FBI history – need not divert this entire mess toward an independent counsel?

“I need to do more research on it,” Collins said in an interview Wednesday. “Obviously, this took me totally by surprise and so I haven’t looked at this issue for years. … I just am not able to give you an answer to that yet.”

Let’s be fair. There are times when such caution is a virtue.

Now let’s be rational. This is not one of those times.

To accept Trump’s claim that he had Comey’s walking papers hand-delivered to the FBI because the director was too rough on Hillary Clinton is to surrender once and for all to the alternate universe that has enveloped the White House these past 112 days.

The man is lying. And with each revelation that undercuts his claim – The New York Times now reports that Comey had just asked for more resources in his search for possible connections between Trump’s campaign and the Russians – Trump looks less like a president and more like a dictator slip-sliding his way toward political oblivion.

Asked if she believed Trump’s claim, by way of Deputy Attorney General Rod Rosenstein, that Comey’s loose lips vis-à-vis Clinton’s emails render him unable “to effectively lead the bureau,” Collins said, “I don’t know what was in the president’s mind.”

But, she added, “If President Trump believes that somehow removing Jim Comey from the job is going to stop the FBI from completing its investigation, or the Senate Intelligence Committee from continuing its investigation, he is completely mistaken.”

Hear, hear. Still, completing investigations is one thing. Finding the cold, hard truth, alas, can be quite another.

The plain reality now is that the entire Department of Justice, including the FBI, is under a cloud.

Yes, the FBI investigation goes on. But no, we can no longer have faith that the fruits of its labor, however rotten they may be, will lead to criminal prosecutions if warranted.

How can we, when Attorney General Jeff Sessions recuses himself from all things Russian in one breath, only to call for firing the guy overseeing the Russian probe in the next?

As for the investigation by the Senate Intelligence Committee, on which both Collins and Sen. Angus King sit, Collins said the pace is only now picking up after weeks of slow going.

Asked to identify the major obstacles thus far, she replied, “It has been difficult to negotiate, with the intelligence community and with the FBI, access to all the individuals and documents that we need.”

Note the word “negotiate.” Special prosecutors don’t negotiate. They compel – and those who stonewall or play cute with them do so at their own legal peril.

Beyond the push and pull among the investigators and their potential targets, there’s an even more compelling reason to anoint a special prosecutor. In fact, Collins herself made that argument quite convincingly as she pondered her next move.

While she has total confidence in Deputy AG Rosenstein, who has served for 26 years in both Democratic and Republican administrations and now presides over the Russia probe, Collins said his reputation might not be enough for a public now aghast at Trump’s latest bombshell.

“I recognize that the public may feel that anyone who’s high up in the Justice Department is somehow tainted,” she conceded. “It’s the timing of the president’s decision and the chaos that has been caused.”

Ah, yes. The timing: All of the transgressions articulated in Rosenstein’s now infamous memo on Comey took place long before Trump took office on Jan. 20.

Yet the memo is dated Tuesday, the same day Trump lowered the boom on Comey.

So inquiring minds now ask: Is Rosenstein indeed the Boy Scout that Collins maintains, or did he get caught up in, as Angus King has suggested, “a solution in search of a rationale?”

Collins, once again, at least grasps the dilemma.

“Let’s say that the Justice Department gets the recommendation from the FBI and decides that there should not be indictments in this case,” she said. “The question for me is, even if that’s the right decision, will the public perceive it as the right decision? Or will they perceive it as a politically tainted decision?”

Let me go out on a limb here and vote for “politically tainted decision.”

The more Collins spoke, the more she sounded like someone trying to talk herself into a decision fraught with political peril.

After all, only one of her Republican Senate colleagues, Sen. John McCain, had by late Tuesday called for a special committee to probe the Russian connection – an option Collins rejects because it would take at least six months just to duplicate the progress already achieved by the Senate Intelligence Committee.

Collins, long assailed by critics who say she talks a good game of bipartisanship only to falter when the time comes to truly stand alone, could change that perception right now. Not with a vote (the decision on a special prosecutor rests with Rosenstein alone), but simply with her voice.

She could continue plugging away from her seat on the Intelligence Committee and, at the same time, ensure that if crimes were committed against our electoral system, they will not be suppressed beneath the weight of Donald Trump’s pathological paranoia.

She could, Senate Majority Leader Mitch McConnell be damned, do the right thing.

“I have a lot of confidence in (Rosenstein) as being professional, a straight shooter, a career prosecutor. The question is, will the public have confidence in him?” Collins wondered aloud. “That’s why I’m looking at those guidelines (for appointing a special prosecutor) – to see whether we’ve reached the tipping point.”

We have indeed, senator. That sound you hear is democracy fast going down the drain.

Bill Nemitz can be contacted at:

bnemitz@pressherald.com