The FiveThirtyEight Senate forecast is holding relatively steady: Republicans have a 61 percent chance of winning control of the Senate in November.
The slight change since our last update — a 1 percentage-point tick toward the GOP — was caused by a Nielson Brothers poll in South Dakota giving Republican Mike Rounds 38 percent, Democrat Rick Weiland 26 percent and independent Larry Pressler 24 percent. The survey found that Rounds could be in trouble in the unlikely event that Weiland or Pressler drop out, but it also gives us more confidence that Rounds is far ahead in a three-way race. He moves up to a 94 percent chance favorite to win the seat.
Besides the South Dakota poll, there weren’t many Senate surveys released in the past day; most of the action was in gubernatorial races instead. Specifically, the polls in Massachusetts are a-changing.
A Suffolk University poll found Democrat Martha Coakley leading Republican Charlie Baker by just 1 percentage point (44 percent to 43 percent). A Western New England University survey showed Baker up 44 percent to 43 percent. And a YouGov survey put Baker up 46 percent to 45 percent.
In the seven polls taken over the past two weeks, Coakley’s average advantage has been just 1.4 percentage points. She led in three polls, trailed in three and was tied in another.
The race is too close to call at this point, and that raises the question: Is Martha Coakley going to blow it again in Yankee blue Massachusetts?
You probably remember Coakley as the Democrat Scott Brown beat in the 2010 Massachusetts special Senate election. A month before that election, Coakley led every poll by at least 25 percentage points.
Earlier this year, Coakley escaped embarrassment by winning the Democratic primary for governor, but she escaped by just 6 percentage points (42 percent to 36 percent). That was despite leading in all but one poll in the month before the primary — by at least 20 percentage points.
Coakley also had a huge lead in early polls for this year’s governor’s race. Her average advantage over Baker from January to June (as calculated by the method described here) was 14 percentage points.
Candidates usually win with early leads this large. Given past polling errors, the average candidate in Coakley’s situation would win close to 90 percent of the time.
Now, Coakley is about even money to win.
As MSNBC’s Steve Kornacki correctly pointed out, three of Massachusetts’s past four elected governors have been Republicans. So, it’s not entirely clear that Coakley is at fault for her vanishing lead. Still, you can’t fault Democrats for feeling a sense of déjà vu.