Forget HR1, the current SCOTUS has five justices who believe Section 2 of the VRA can't even be used to challenge racial gerrymanders, although such a case hasn't made it to SCOTUS yet.
Well it's hard to say. Voting against something popular vs as the fifth vote is different. O'Connor may be the sixth vote to struct down Roe, but not fifth. This is also why Kennedy is much more liberal in popular issues when he was the median justice after O'Connor retire. Same for Roberts.
For HR1, I guess Thomas and Alito will strike it down, Gorsuch very likely as well, but not sure the other three.
Roberts will bend to political pressure. It seems the pressure to preserve HR1 will be no less than Obamacare, or at least much more than the Shelby case, in which he was the forth and not the critical fifth vote. Now if it was up to Roberts himself, he will likely be against it, as he cares about the reputation more than anything else. But if there are already 5 votes, I am not sure if he would prefer a 6:3 to 5:4.
For Barrett, I am not quite sure. If I were Trump, I would nominate Barbara Lagoa, who is clearly more partisan than Barrett. Barrett is probably a religious hard right, so not friendly with abortion and LGBT, but not very partisan, as compare to Scalia for example. Actually, judging from her experiences, she may be the least partisan conservative justice. (O'Connor, who is much more liberal than her, is actually much more partisan, as she strongly identify as R and do care about the interest of the party a lot.) I personally feel nominating her is a triumph for the religious right, but a mistake for R. She may be willing to scrap Roe and Obergefell v. Hodges, which will be electoral disaster for R, while not eager to protect critical R interest in things like voting.
Then there is Kavanaugh. He is an enigma to me. He changed positions wildly in the months around past Nov regarding voting. He may not be as conservative to things like abortion, but judging from his past experiences, he should be quite partisan. But it gives me the impression that he also cares the reputation of SC, although not to the extent of Roberts, based on which cases SC pick up.
So R only has three votes, and they cannot lose Kavanaugh and Barrett. I think Kavanaugh is more likely than not to be the forth. So it ends up with Barrett. Or Kavanaugh may be persuaded by Roberts to protect the reputation of SC.
