The math was never on the GOP’s side. Republicans enjoy a 53-47 majority in the U.S. Senate, but the party’s defending 23 of the 35 seats up for grabs in the chamber this November. And while at least a half-dozen GOP seats are considered battlegrounds, Democrats are defending just a handful of vulnerable incumbents. Two developments this month appear to be giving the Democrats a further boost. “I do think it’s 50/50 right now. I think that Democrats' odds have improved over the past month,” predicted Jessica Taylor, who closely tracks the Senate races for the Cook Report, a leading...