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National chatter about a potential wave election has persisted since at least the spring of 2017, and conventional wisdom for the past 18 months or so has been that Democrats will take control of the U.S. House, but struggle to take control of the U.S. Senate because they have to play too much defense.

As we’re now within 100 days of the election, speculation will quickly crescendo as pundits attempt to discern what kind of wave, if any, might be approaching our electoral shores. In the midst of such an environment, “What constitutes a wave election?” is a question that rarely gets asked, as most settle for the ambiguous expectation of big gains for the party out of power. Meanwhile, “What does this mean for down-ballot races in Indiana?” is a question that rarely gets answered, at least not in a way that achieves consistent consensus. But by investigating the former question, we have a better chance of using historical data to attempt to answer the latter.

While political scientists have no widely-accepted definition of a wave election at the national level, most of the focus tends to be on the net-change in seats in the U.S. House since all 435 seats are on the ballot each year (as opposed to the U.S. Senate, where only 1/3 of the seats are up in any given election; or the presidency, which is only on the ballot every other cycle). Additionally, smaller districts in U.S. House races (as opposed to state-level results in U.S. Senate and presidential races), provide a more nuanced view of national sentiment on current governing policies.

Stuart Rothenberg, arguably the most respected national handicapper, uses a 20-seat net gain in the U.S. House as his cutoff for a wave election; this number seems reasonable and despite disagreement probably comes closest to anything resembling consensus. But while the U.S. House number might be the most important factor, let’s also stipulate (as do many political scientists) that the following conditions also be met: 1.) The party that gains 20+ seats in the U.S. House must also make some gains in the U.S. Senate; 2.) If there is a presidential race on the ballot, that same party must win the presidency.

Over the last 50 years those criteria leave us with seven wave elections: 1974, 1980, 1982, 1994, 2006, 2008, and 2010. So far, so good: Even without our criteria, most observers would probably settle on those same elections.

So, did we see similar waves in Indiana in those years? Let’s adapt our criteria a bit: 1.) The wave party must have a five-seat net gain in the Indiana House (20 out of 435 seats in the U.S. House is about 5%); 2.) The wave party must pick up at least one seat in the Indiana Senate; 3.) The wave party must win a majority of the statewide executive offices on the ballot. Under these corresponding criteria, only 1974, 1980, 1994, and 2010 saw the wave wash upon our Hoosier shores.

In 1982, we saw Democrats pick up six seats in the Indiana House and three in the Indiana Senate, but they only won one of the three statewide executive races that year (additionally, the only partisan change in Indiana’s Congressional delegation was the loss of a seat through reapportionment, which meant the Democratic advantage declined from 6-5 to 5-5).

In 2006 and 2008 combined, we saw Democrats gain 52 seats in the U.S. House, but only three in the Indiana House (all in 2006, which was enough to give Democrats control of the chamber, but not in overwhelming fashion) and none in either cycle in the Indiana Senate. Meanwhile Republicans swept all statewide executive offices in those cycles. Even as Barack Obama became the first Democratic presidential candidate in a generation to carry the state in 2008, there was no gain for Democrats anywhere in the Statehouse.

That’s not to say state-level Democrats won’t pick up seats in an environment that could produce a national-level wave, only that recent Democratic waves that upended Washington – with the exception of the Watergate-fueled wave in 1974 – haven’t translated to Indianapolis.

But this isn’t just a Democratic wave year phenomenon: If you look at all elections since 1970, there is very little statistical correlation in national and state legislative outcomes. On a scale of -1 (perfect negative correlation) to +1 (perfect positive correlation), comparing U.S. House to Indiana House outcomes yields a coefficient of 0.48. That indicates there may be some weak positive correlation, but not much. Comparing the U.S. House to the Indiana Senate, or the U.S. Senate to either Indiana chamber, yields a result much closer to 0, which indicates virtually no correlation at all.

While this might seem counter-intuitive, it makes some sense on several levels. First, Indiana has long been a conservative, Republican state (even when it elects Democrats, they have typically been conservative Democrats). As much as anything, that probably explains why Republican wave years like 1980, 1994, and 2010 seem amplified at the Statehouse, while Democratic wave years like 1982, 2006, and 2008 have seem muted.

Second, the partisan lean also means that Republicans have the upper-hand in drawing legislative maps; when Democrats have controlled the process for the Indiana House, the state’s partisan demographics made it difficult to create a huge advantage. In fact, because Democrat-drawn maps tended to create a higher number of competitive districts rather than solidly Democratic districts, this also could explain why a Republican wave election would be amplified instead of muted.

Finally, it’s worth noting that the dynamics that often create national waves just aren’t present at the state level. Many times, for instance, the party out of power is aided by a high number of open seats in the U.S. House, such as the 36 open Republican-held seats this cycle caused by retiring members, many of which are competitive districts. Meanwhile, the Indiana House will see only six open Republican-held seats caused by retirements (Friend, Richardson, Beumer, Culver, Washburne, and Baird), most of which are fairly safe Republican seats.

Again, that’s not to say state-level Democrats won’t pick up seats. In 1974, the national environment bled over in a big way as Indiana Democrats netted 28 seats in the Indiana House (though it’s worth noting that Republicans had picked up 19 seats in 1972 and held a 73-seat supermajority, so there was a bit of a perfect storm to flip so many seats in one election). With political polarization extremely high in 2018, it’s not yet clear that the national environment would be enough to produce a Watergate-level wave at the federal level, let alone the state level.

But history tells us that a 1982- or 2006-like outcome at the state level is more probable anyway. Even though it didn’t resemble a wave, Democrats picked up three Indiana House seats in 2006, which was enough to take control of the chamber. So, while even a large national wave this year probably won’t put control of the Indiana House in play, even a muted impact that leads to a small net gain of seats could be enough to break the Republican supermajority.

Meanwhile, the Indiana Senate is likely to be more immune to the national environment: If Democrats manage to win one Republican-held seat in the Indiana Senate, it would be the first time in 20 years they’ve done so; if they win more than one seat, it would be their first time since 1984. The same goes for the secretary of state, auditor and treasurer races on the ballot, which Democrats haven’t managed to win since 1990, 1982, and 1970, respectively.

So, while the historical data may not give us a precise expectation for Indiana’s state elections in 2018, it does provide guidance: If there is a national wave that favors Democrats, it’s not unlikely we’ll see some gains for Democrats at the Statehouse. But you should still bet against a state level wave.