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Could Clinton’s Coattails Cut Both Ways?

New research finds a popular presidential candidate can help elect members of Congress — unless the election is seen as a blowout.

By Tom Jacobs


Hillary Clinton greets supporters at a campaign rally in Pittsburgh, Pennsylvania. (Photo: Justin Sullivan/Getty Images)

In yet another strange twist in this oddest of elections, polls late last week suggested that, even as the presidential race was tightening, the odds were increasing that the Democrats would regain control of the Senate.

On the face of it, this makes no sense. According to conventional wisdom, the smaller Hillary Clinton’s margin of victory is in a given state, the shorter her metaphorical coattails will be, which means down-ticket Democrats will have a tougher time getting elected.

But research published earlier this year suggests the reality is more complicated than that. Columbia University political scientist Robert Erikson examined the relationship between presidential and congressional voting, focusing on the House of Representatives. He discovered a push-pull dynamic.

“The national Democratic vote for the House increases with the Democratic vote for president,” he writes in the journal Legislative Studies Quarterly, “but decreases with the Democrats’ perceived chances of winning the presidency.”

If her election is a foregone conclusion, it will lead to a backlash in which many voters decide they’d better check her power.

In other words, the coattail effect is real. But when the outcome of the presidential race seems fairly certain, this likelihood inspires in some voters a reluctance to give the winner total power. Driven by this impulse (which he suspects is conscious for some, unconscious for others), they cast their congressional ballot for the opposing party.

Erikson came to this conclusion after statistically modeling the congressional vote in all 17 presidential elections between 1948 and 2012. He used “the gambling odds from betting markets as reported on election eve” to estimate “knowledgeable voters’ perception of the probability that a Democrat rather than a Republican is about to be elected president.”

As expected, he found that “the electorate’s support for a congressional party increases in proportion to its support for the party in the presidential contest” — the famous coattail effect. But he also found “the electorate tends to punish the (incumbent) presidential party, and also the party favored to win, in proportion to the certainty of its election.”

Not surprisingly, he found the latter effect is most prominent among high-information voters who identified themselves as moderates and/or independents.

Erikson is careful not to overstate these results. “Coattails contribute more to congressional election results in presidential years than does anticipatory balancing,” he writes. But the latter phenomenon is real, and it helps explain why the coattail effect is often smaller than predicted.

The clear implication is that, now that the Clinton-Trump race is seen as surprisingly close (a perception that may or may not be accurate), the impulse to vote for Republican congressional candidates to check Clinton’s power gets dampened.

For a moderate conservative in Missouri, it may be more tempting to vote for that intriguing Democratic Senate candidate who can assemble an assault weapon blindfolded if you think Donald Trump has a good chance of becoming president.

So, to stretch a metaphor way beyond its breaking point, coattails are a double-edged sword. Yes, a popular presidential candidate will lead more people to vote for her party’s other candidates. But if her election is a foregone conclusion, it will lead to a backlash in which many voters decide they’d better check her power.

So, for Clinton, a close presidential race — or at least the perception thereof — may not be such a terrible thing after all.