A new occupant of McCain’s seat is good news for McConnell, Trump and Republicans who want the party to largely follow the edicts of those two GOP leaders. McCain was largely absent from public life while he was receiving treatment for brain cancer, and during that time, the Senate was split 50-49 in favor of the GOP. That meant one Republican defection could kill any bill. With 51 active Republicans, one defection still left room for Vice President Mike Pence to cast a tie-breaking vote in favor of McConnell and the president. With 50, Pence’s vote isn’t enough as long as one Republican sides with the opposition.
With the addition of a reliable McConnell ally, the Senate’s partisan breakdown returns to 51-49, giving Republican leadership some breathing room. Retiring Sen. Jeff Flake of Arizona, a Trump critic who occasionally bucks party leadership, will have less power to stall Senate GOP initiatives. That could help the party get more federal judges appointed, a big priority for Trump and McConnell. (I don’t think the return to full strength in the Senate will mean much for other issues, because the Republicans aren’t really trying to push through major initiatives before the midterms.)