Tonight in Ohio, Republican voters could end — or come close to ending — the GOP presidential primary. But that’s not the only important primary going on in the Buckeye State.

Democratic Reps. Marcy Kaptur and Dennis J. Kucinich's districts were merged into one. (Amy Sancetta/AP)

The new 9th district takes about 47 percent of Kaptur’s Toledo-based district and only 40 percent of Kucinich’s territory, giving Kaptur an edge. She’s also been in office over a decade longer than Kucinich — 14 terms, meaning she’s in line to helm the powerful Appropriations Committee.

Kaptur has ably hammered on Kucinich’s flirtation with a bid in Washington state instead of Ohio — one of her radio ads compared him to LeBron James.

On the other hand, Kucinich’s Cleveland home base was left intact and he has a national support network thanks to his two presidential campaigns.. He’s reminded voters repeatedly of Kaptur’s votes for the wars in Iraq and Afghanistan. He also has some big fans, including Willie Nelson and Russell Simmons. (Kaptur has Tom Hanks and former Republican Sen. Bob Dole.)

There are, as always, complicating factors. A Cleveland entrepreneur named Graham Veysey is also in the race, taking shots at both "Congressman Status and Congresswoman Quo." He’s expected to win about ten percent of the vote. The Campaign for Primary Accountability, a Houston-based super PAC funded in part by conservative activists, has taken Kucinich’s side against Kaptur.

“We feel that Dennis Kucinich is the more independent voice,” CPA spokesman Curtis Ellis told The Fix. “He bucks the party leadership.” Veysey, he said, “didnt seem like a credible candidate.”

There haven’t been any polls here, while conventional wisdom suggests Kaptur will win, nasty radio ads from her campaign have some wondering if her internal polling shows trouble.

“You have to ask yourself whether this race is a lot closer than anybody thinks, or whether Kaptur’s people smell blood and understand that she could put him away,” Cleveland consultant Bill Burges told The Hill.

“It was never our intention to go negative. It never even occured to us,” said Kucinich spokesman Andy Juniewicz. “We’ve been as positive as we can be except to respond to the attacks by the Kaptur campaign.” As far as the super PAC goes,

One Kaptur radio ad that Kucinich’s campaign has singled out as particularly egregious attacks him for praising Jimmy Dimora, a former county commissioner now on trial for racketeering. Kucinich’s embrace of Dimora came years before the scandal broke.

Kaptur supporters, however, expressed nothing but confidence.

“It’s going to be relatively close, but we think Marcy’s in good shape,” said former state party chairman Jim Ruvolo, a Kaptur supporter. “I think Marcy will do better in Cleveland than Kucinich will do in Toledo.”