Many Mainers understand they have much to lose with the proposed legislation. But voting against the bill achieves nothing if the legislation passes because Collins and Paul vote no and 50 Republicans vote yes while Pence breaks the tie. That would mean that Collins succeeded in jockeying for position for one of the two available "No" vote spots and maintain the optics of "doing everything she could" on behalf of her constituents. But that is only optics, not reality. Collins could do more.
Collins could change parties. She could join the Democratic Party as a true conservative. This would send a loud message to Mitch McConnell that moderate Republicans are not going to put up with all of his shenanigans and he would have to reassess the metrics he currently uses to craft legislation. The Trump administration is incredibly extreme in every respect. Collins could use this moment in history to send a clear message that with Trump as the head of the Republican Party, she can no longer be a "Republican", but she is still conservative and will be a conservative Democrat. Switching party allegiance would give her leverage with the Democrats if they regain the Senate anytime soon. Granted, such a tactic might not have much chance if no moderates join her and Democrats continue to struggle at the polls.
As a moderate, willing to go along to get along, Collins would never do anything like joining the Democratic party. But she could also change parties by becoming an Independent in the Senate for the same reasons. Challenge McConnell's leadership. Challenge Trump's
New England has a tradition of moderate Senators who change parties for a variety of reasons. Arguably switching parties in New England is more palatable to the constituents than in other parts of the country where it may be unthinkable, like Ohio. And certainly Mainers like to think of themselves as independents.
Collins need look no further than fellow Maine Senator Angus King(I) who caucuses with the Democrats. King has explained that he caucuses with the Democrats because Maine already has a Republican Senator and this gives Maine the best chance to have their interests represented. I am not sure I believe that is the reason, but it may be a reason.
Joe Lieberman comes to mind as someone who traveled in the opposite direction, from (D) to (I), technically Independent-Democrat) along a convoluted path that had him still caucusing with the Democrats, but operating always with the threat to go over to the Republicans at any moment. Anyone who watched the Vice Presidential debate in 2000 between Cheney and Lieberman could be forgiven for wondering if they were running against each other or on the same ticket.
The Jim Jeffords switch in 2001 from Republican to an Independent who caucused with Democrats provides one model of a successful switch. The Jeffords switch shifted the balance of the Senate. It works better the closer the Senate is to 50-50. With the VP a Republican, three Senators would need to cross party lines.
And yes, any such action by Collins is incredibly unlikely. She showed her true colors a year ago by maintaining the optics of reasonableness - as a Republican willing to meet with Merrick Garland following his appointment to the Supreme Court, while doing nothing within her power to change how the Senate operates.
So, instead of "Stay Strong Susan!", but being passive, the chant should be "Become Powerful Susan!". "Make a difference: while you still can.
Collins is expected to run for Governor of Maine in 2018. The current governor is very much like Trump. Collins would be leaving the Senate to save her state, which is laudable, but why not think big? Save your country first, or at least move your country in a better direction.
As times become more and more extreme, continuing to function as a moderate eventually turns you into a radical. If you refuse to consider all tools at disposal, others will be happy to employ all tools at their disposal to take advantage of that weakness.