One of the enduring memes in politics is that the Presidential party really takes it on the chin in the midterms in Year 6 of a Presidency. People get tired of the incumbent, scandals inevitably reach critical mass, and the President's party pays the price.
The main objection raised against this alleged truth is: what about 1998? The answer is always: it was a special case, what with the Republicans impeaching a President that the public supported.
But I just don't think there's actually a pattern, just the illusion of one. Here's my argument:
I'll be 60 when the 2014 midterms roll around. (I hardly feel that age, I'm glad to say. Moving on...) During my lifetime, all nearly 60 years of it, there has been only one Democratic President to reach Year 6 of his Presidency. That President, of course, was William Jefferson Clinton, and his party lost no ground in the 1998 midterms, despite a major scandal that was the culmination of six solid years of the hunting of that President.
If one wants to bend a rule and treat Kennedy-Johnson as a single Presidency, you could point to 1966 as well. I don't buy that: I remember 1966, first of all, and it just doesn't fit the mold. LBJ had been President for only 3 years (and had been practically invisible as Veep), so people weren't tired of him. There wasn't a critical mass of scandals: sure, Bobby Baker, Billy Sol Estes, but no sense that they were more than peripheral. And the 1966 midterms were more a reversion to the mean after the GOP's Goldwater debacle in 1964, than a public upset with the President.
Meanwhile, on the Republican side, what do we have in sixth-year Presidencies?
When it comes to scandals, we have the real thing: Watergate in 1974, Iran-Contra in 1986, and pretty much everything in 2006. And in the last case, a public that had thoroughly had enough of George W. Bush.
You've got to go back to Eisenhower to get a 'typical' sixth year. Minor scandals by today's standards (Sherman Adams), a mild recession, a sense (that Kennedy would soon take advantage of) that perhaps the old general had lost his energy with age...if there's a genuine year-six jinx that's independent of truuly major scandals and Presidential fuckups, this is your only data point in the past six decades to back it up.
And (a) one data point isn't a pattern, and (b) 1958 was a long time ago. The world has changed a bit since.
Not to mention: if there's a pattern emerging in recent Democratic administrations, it's to screw the pooch electorally in Year 2, and to only gain minimal ground back in Year 4 while holding onto the Presidency.
IMHO, the real reason why the GOP didn't and couldn't blow it open in 1998 was that there was little room for them to have another blowout, after having just had one in 1994. I suspect the same is true for Obama in 2014: the GOP picked up most of the marginal seats there were to win in 2010, and just don't have a target-rich environment in the House in 2014. (They do in the Senate, but potential quality challengers are shying away in droves from running for Senate in 2014.)
But I don't think there's any clear pattern that says a President's party has to get its ass kicked in Year 6. The immediate circumstances will tell, not any overarching pattern. What the Dems have to worry about in 2014 is getting their base to show up, given that midterm voters tend to be older and whiter than the electorate in Presidential years, not scandal and sixth-year public fatigue with the President.