Pre-rollout polls showed New Hampshire incumbent Jeanne Shaheen with double-digit leads over state Republicans. But she led former Massachusetts Sen. Scott Brown by only 48-44, and Brown now seems interested in the race.
Obama carried Michigan 54-45 in 2012. But a Democratic poll this month shows Republican Terri Lynn Land leading Democrat Gary Peters 42-40. Neither is well-known. But the Republican label seems surprisingly strong in a state where Republicans have won just one Senate race in the last 40 years.
So Republicans have plausible chances to gain as many as 11 seats. But there are countervailing factors.
Republicans nominated some astonishingly weak candidates in winnable races in 2010 and 2012, and Democrats hope they will do so again in Georgia, where Michelle Nunn, daughter of former Democratic Sen. Sam Nunn, has been running roughly even with -- or a bit ahead of -- various Republicans.
And Democrats have hopes of depicting Senate Minority Leader Mitch McConnell as a Washington insider and toppling him in Kentucky, despite the state's anti-Obama leanings.
That being said, National Journal's survey of Washington political insiders shows most Republicans and a near-majority of Democrats predicting a Republican Senate majority. That's noteworthy, because these insiders, who spend so much time with incumbents, didn't predict party takeovers in 2006 and 2010 at this point in those election cycles.
The Obamacare rollout has also shifted opinion on the generic vote -- which party's candidate do you support for the House of Representatives? When the shutdown ended, Democrats led 47-41 in Real Clear Politics' average of recent polls.
Now, Republicans lead 44-41 on the question that has often underestimated actual GOP performance. Analysts Stuart Rothenberg and Larry Sabato see more than 20 Democratic House seats at serious risk.
All this could change if public opinion on Obamacare -- or Obama -- shifts once again. But it looks like recent obituaries of the Republican Party were premature.