Quinnipiac University polling shows that voter self-identification has shown a lot of movement since early 2015, when 28 percent of registered voters called themselves independents. In their most recent poll, that number is at 38 percent. Over the same period, the GOP’s percentage of the electorate has dropped seven percentage points, while Democrats have remained static in the 29–32 percent range.

 

Right now, polling for independents is all over the place. An April 8–11 NBC News/Wall Street Journal poll had Democrats up 11 percent with independents. That same month, a Quinnipiac University national survey showed Republicans with a two-point advantage among independents. And a May 2–5 CNN/SSRS survey found that independents preferred Democratic nominees for Congress over Republicans by three points.

A recent Morning Consult poll dove a little deeper into the independent vote and found that how they end up voting is still in doubt. Democrats have an eight-point lead with those who have already made up their mind, but a 40-percent plurality is still undecided and leaning equally between both parties, which means that about 15 percent of voters are up for grabs. The Cook Political Report says that 37 Republican-held congressional seats are tossups or worse from the Republican perspective, and Democrats only need to win 23 of them to take control of the House of Representatives. What side these 15 percent of voters come down on could determine control of Congress.

 

Independent voters have often made a huge difference in recent midterm elections, according to Roll Call’s Stuart Rothenberg. In the Republican wave years of 2014 and 2010, independents backed Republican candidates by 12 and 18 percentage-point margins, respectively. In 2006, independent voters sided with Democrats by an 18-point margin. So far, we’re not seeing that with independent voters, but they are notoriously late about making up their minds.

So what do they want? The president is influencing these voters, but what is at the top of their list are economic issues, and they’re not seeing much difference between the parties on trade, supporting small businesses, and caring about the middle class.

 

And right now, neither party is paying particularly close attention either to independent voters or their economic agendas, mostly because both parties have been engaged in primary elections to select their own nominees. We’ve seen Republicans abandon their economic message for an immigration one that better motivates their base vote, while Democratic primary voters want to hear about health care. Right now, neither party is focused on what undecided independent voters are waiting to hear. As we leave primary elections behind and begin to see campaigns communicate for general-election voters, whichever party most effectively communicates a persuasive economic message has a good chance of winning these independent voters — and the election.

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Jack Martin is the global chairman and chief executive officer of Hill+Knowlton Strategies (H+K), a multinational strategic communications firm with clients constituting half of the Fortune Global 500 list with more than 80 offices around the world.