In 2016, I promised to get away from giving you probabilities. Here I show that under current conditions, you can optimize your donations without such calculations.

As has been the case in past elections, I’d like to point out key races where supporters of either Democrats or Republicans will get the maximum impact for their donation. (I’m assuming that control of either chamber of Congress has comparable value – see reader James McDonald’s point.)

This year, I don’t recommend giving to House races for two reasons.

There are just too many of them. Over 80 districts are less Republican-leaning than Ohio’s 12th district, whose margin was razor-thin in the recent special election. Compared with the six key Senate races I’ve listed at left, your donations would be diluted by more than a factor of 13. This is the big reason.

Under current conditions, we are closer to threshold for switching Senate control than for switching House control. Therefore Senate control is closer to the knife’s edge.

Taken together, these two reasons dilute the impact of your donation by a factor of 30-100*. This can change, depending on how the overall odds of House or Senate control change over the next two months.

Instead of giving you probabilities, which leads to possible complacency, I will simply ask: how far are Democrats/Republicans from threshold for House or Senate control?

In regard to effective giving, start with individual races. Once the margin between two candidates gets beyond about 5 percentage points, the probabilities get saturated. Money and activism don’t really move the needle. Instead, it is more strategic to look for races that are closer to threshold. Giving to, say, Dianne Feinstein’s re-elect campaign would be a waste of money. The same would be true for giving money to Senator Roger Wicker – again, no point. But the Nevada Senate race between Jacky Rosen (D) and incumbent Dean Heller (R) – now there’s a close race.

The same logic applies to House and Senate control. But now we have to both identify close individual races, and also ask where the chamber stands as a whole. Here are some examples of my quantitative analysis from 2014 and 2012.

With all that in mind, here is some information about 2018.

I estimate that for Democrats to have an even-odds chance to take control of the House, they would have to win the national popular vote by about 6 percentage points. I like to look at two indicators that reflect real voter behavior at a national level: special elections (i.e. real voting) and the generic Congressional ballot question (i.e. opinion polls).

Midterm opinion polling is hard to do accurately, and was five points off in 2014. Also, it can change over time. So let me put that aside until a later post.

In special elections since 2016, Democrats have outperformed Hillary Clinton’s performance against Donald Trump by an average of 11 percentage points. She won the popular vote by 2 percentage points, so if this pattern were applied to the whole nation, it would translate to a 13-point popular margin. That would be the biggest margin for either party since the post-Watergate year of 1976, when Democrats won the national popular vote by 13.6 points (and before that, 17 points in the Watergate year of 1974). Historically, special election performance has been within about 6 points of the mark, so we could expect to see a margin of 7 to 19 points this fall.

Thirteen percentage points is a lot. Even a margin half as large would still be enough to switch several dozen seats from Republican to Democratic, and make Democratic control likelier than not. Because 13 points is 7 points above the magic threshold, I’d give Democrats a handicap (to use golf terminology) of 7 percentage points favoring them.

The Senate is considerably closer to the knife’s edge.Senate control is said to be a difficult challenge for Democrats. However, the eventual seat margin will be close, and the number of critical races is small. If we look at current polling margins, a swing of 3 points would be enough to put Democrats on the brink of having 51 seats. So in the Senate, Republicans have a handicap of 3 percentage points favoring them.

I should throw in here that close Senate races tend to break mostly in the same direction on Election Day. Which way they’ll break isn’t known; one way gets Democrats to 51-52 seats, and the other way gets them to 45-46 seats. It appears that Senate control could go either way.

Bottom line, Senate control is on a knife’s edge more than House control. I could convert that to probabilities, but my feeling is that does not have a clear benefit. (Ballpark, it’s 0.9 for Democrats in the House, 0.7 for Republicans in the Senate.) For now, I will go out on a giant limb and say that the basic reason for paying more attention to the Senate is

7 > 3.

By the way, longtime readers of PEC will recognize these quantities as being conceptually related to the meta-margin, which I have calculated for Presidential races. To give you an idea of uncertainties in this quantity in tight situations, the meta-margin was around Clinton +1.3% in 2016 and ended up as Trump +0.7%, a 2-point error that was highly consequential.

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In addition, I have added governor’s races. I focus on one race: Wisconsin, with Tony Evers (D) challenging the incumbent, Scott Walker (R). This is a long-term investment. Governors elected this year will oversee redistricting in 2021. Of the Egregious Eight gerrymandered states, Wisconsin is the one state where the governor’s office is the only identifiable route to attaining fairer districting. (For other close governor’s races, Larry Sabato’s Crystal Ball estimates include Colorado, Florida, Minnesota, and Ohio).

Still thinking about the House? That’s good – this is no year for giving money and leaving it at that. This is a year for getting out there and doing everything you can. I suggest a two-prong strategy: (1) give money to national Senate/governor races (key races are listed at this ActBlue site for Democrats; Republicans can give directly to the NRSC), and (2) engage in personal get-out-the-vote activity in a district near you. Find a competitive district near you using this tool!

As I wrote above, I don’t recommend donating to House races. I guess an exception is close races in Florida, where increasing turnout in a Congressional district also moves the statewide Senate vote. So…Florida districts 18, 26, and 27.

*Making this calculation accurately requires using probabilities. Many considerations could go into it , such as estimating probability distributions and advertising costs.