So much for the emerging democratic majority: Megan McArdle says that the GOP has a 70 percent chance of holding the House, Senate, and Presidency after the 2016 election. McArdle is basically right about the House—that’s GOP turf—but the rest is way off. Let’s take the Presidency, the Senate, and the math step by step.

**The Presidency**

McArdle thinks that the Democrats are going to lose the presidency because parties don’t hold the White House for three consecutive terms. In my view, this is a bit more myth than reality. Let’s take a look at the post-war elections after an incumbent president leaves office after two or more terms.

A lot of people look at these numbers and see some sort of anti-incumbent curse, especially since the challenger technically won the 2000 election. What I see is a bunch of close elections: 2000, 1976, 1968, and 1960 are the four closest elections of the last century. 1948 was a pretty close election too—Dewey beats Truman close. I think all five of these elections could have gone the other way. The two elections that weren’t close seem like relatively predictable blowouts. The less predictable blowout was probably 1988, the one where the incumbent party did pretty well.

So I think the most reasonable thing to expect is a pretty close race in 2016. No one will have the advantage of incumbency, and therefore you get a pretty level playing field—save particularly favorable or unfavorable economic conditions. Even if you’d give the challenging party an edge, it should only be a slight one—slight enough to be overwhelmed by a Clinton candidacy or a demographic trump-card, which might wind up giving the Democrats a slight edge heading into 2016. But since the economy is still the biggest variable, it’s tough to give either side much better than a 50 percent chance, unless you’re much better at predicting future economic growth than, say, economists.

**The Senate**

Democrats will have 55 seats in the Senate after Cory Booker wins New Jersey’s Senate seat. McArdle seems to concede that the GOP probably won't take the Senate in 2014, but maybe they can get up to 48 or 49 seats. That's probably about right.

But 2010 was a rout, so there just aren't very many competitive Democratic-held seats up in 2016. Absent retirements, there might not be a single Democratic-held "toss-up" seat in the initial 2016 senate ratings. Conversely, the GOP will have to defend vulnerable seats in Illinois, Wisconsin, Pennsylvania, or potentially New Hampshire or Ohio. So if McArdle doesn't think the GOP is favored to take back the Senate in 2014, there's basically no way to argue they have a 75 percent chance in 2016. Let's say that the GOP has a 23 percent chance of controlling the Senate in January 2017—a 30 percent chance of taking back the Senate in 2014, and then a 75 percent chance of holding onto it in 2016.

**The Math**

If we assume Republicans have a 100 percent chance of winning the House, a 50 percent shot of winning the presidency, and a 23 percent shot of holding the Senate in 2016, then, at most, they have a 23 percent chance of holding all three branches. But for that to be true, they’d have to win the presidency in every scenario where they won and held the Senate. That's not realistic. Their real opportunity to take the Senate comes in 2014, not 2016, so it’s conceivable that Democrats could have a pretty rough 2014, but still win the presidency two years later, even in scenarios where they don't retake the Senate. That said, the two possibilities aren’t completely independent, either: surely if things go bad for Democrats in 2014, there’s a better chance they go poorly in 2016. But as 2010 taught us, that’s no sure thing—especially since 2014’s competitive Senate seats are on red turf. On balance, let’s say there’s a 55 percent chance that if the GOP takes back the Senate in 2014, they win the White House *and* retain the Senate. That strikes me as a little high, but whatever. If you agree, there's something like a 16 or 17 percent chance of holding all three branches of government in January of 2017.

This is all for illustrative purposes and it isn't close to perfect. These numbers are outright arbitrary. Some numbers are just missing: Surely the Democrats have some chance of winning the House, and surely the GOP has some shot to take back the Senate in 2016, even if they don't win it in 2014. But the point is that the GOP doesn't have anything close to a 75 percent chance of holding all three branches by 2017. Not even close.