Chief Justice John Roberts privately lobbied fellow conservatives to save the constitutional right to abortion down to the bitter end, but May's unprecedented leak of a draft opinion reversing Roe v. Wade made the effort all but impossible, multiple sources familiar with negotiations told CNN.

It appears unlikely that Roberts' best prospect -- Justice Brett Kavanaugh -- was ever close to switching his earlier vote, despite Roberts' attempts that continued through the final weeks of the session.

New details obtained by CNN provide insight into the high-stakes internal abortion-rights drama that intensified in late April when justices first learned the draft opinion would soon be published. Serious conflicts over the fate of the 1973 Roe were then accompanied by tensions over an investigation into the source of the leak that included obtaining cell phone data from law clerks and some permanent court employees.

In the past, Roberts himself has switched his vote, or persuaded others to do so, toward middle-ground, institutionalist outcomes, such as saving the Affordable Care Act. It's a pattern that has generated suspicion among some right-wing justices and conservatives outside the court.