(CNN) - The union vote is a key reason why the race in Ohio is so competitive.
Obama has many of the major union endorsements, including the Teamsters and the Service Employees International Union. But as in Nevada, some union members may not have necessarily followed their leadership’s endorsement.
Union members – who made up nearly one-third of Ohio Democratic primary voters - broke for Clinton 52 to 47 percent. This is good news for Clinton, who aggressively targeted union households over the last several weeks. Her campaign spent the past few days trying to draw attention to slleged remarks from Obama’s economic adviser that seemed to imply the candidate might not be as committed to changing NAFTA as he said he was.
If Clinton goes on to win Ohio, she'll owe union members there a big thank you.
CLARIFICATION: The exit polls do not show which unions Obama and Clinton supporters are from.
Change to Win, the union organization that includes the Teamsters and SEIU, reports their mobilization efforts were pivotal in tightening the race in Ohio.
"In the past ten days the Change to Win unions’ education and mobilization efforts tightened the race in Ohio and closed the gap on the 20 point lead Sen. Clinton held just a month ago," Change to Win spokeswoman Noreen Nielsen said. "A Mason Dixon poll conducted as recently as Friday (2/27-2/29) had union households supporting Senator Clinton by 56-37. As early reports indicate, if the marginal lead Sen. Clinton currently has among union members holds, we clearly closed the gap and shifted a significant number of union members to support Sen. Barack Obama."
- CNN Senior Political Analyst Bill Schneider