So What. Chris Cillizza

The simple fact is that for Tester to win, he is going to need to over-perform the top of the ticket by 15+ points. And that, no matter his political skills, is very hard to do. And/but: Other top handicapping sites like the Cook Political Report with Amy Walter and Inside Elections with Nathan L. Gonzales still have Montana as a pure “toss up”

The practical effect of the Tester move is that, according to the Center for Politics, there are now 51 Senate seats that are solidly, likely or leaning for Republicans. Which means that if all plays out as the UVA handicappers expect, the GOP will control the Senate in 2025.

Which is a very big deal. If Harris wins the White House, a Republican-controlled Senate would force her to moderate her agenda significantly. If Trump wins, a GOP Senate would, well, just look at the Supreme Court’s current composition to see how much that could matter.