“The biggest effect of these allegations will be that they will give Democrats like McCaskill and Heitkamp and Tester the cover that they will need to vote against Kavanaugh. They can’t justify a vote against him based on qualifications; but they can say they can’t vote for him based on character.”
It’s a win-win tactic for the Rats: Get the confirmation delayed until after the midterms; or, peel off two or three potential “yes” votes. Either way, the Rats win. That’s why they pulled this stunt.
No other reason I can think of.