AVON LAKE, Ohio — Mitt Romney's campaign called the US presidential race in key toss-up Ohio a "dead heat" Monday eight days before the election, claiming the Republican was poised to win the state after vital recent gains.

In a morning memo, Romney's Ohio state director Scott Jennings said a bolstered Romney ground game and newfound support for the Republican nominee in the Midwestern state was creating a "nightmare" scenario for President Barack Obama in the run-up to November 6.

"The state of the race in Ohio shows a dead heat, with Romney tracking toward victory on Election Day," Jennings wrote, citing an Ohio newspaper group poll released Sunday that pegged the race as tied at 49-49 percent.

In the past two weeks, the Romney campaign has knocked on 669,534 doors, while early voter Republican turnout is higher this year than in 2008, and early voting among Democrats is down, he wrote, quoting former George W. Bush's 2004 campaign voter expert Adrian Gray.

"We aren't doing anything differently to promote the events," according to Jennings. "People are just organically showing up to see the next leader of the free world.

Romney and Obama are both pouring vast resources into the Buckeye State, which has emerged as perhaps the key battleground of the entire election.

No Republican has ever clinched the White House without winning Ohio, and Romney spent all of Sunday campaigning here.

On Monday he hosted a rally with 5,000 supporters at a high school in Avon Lake, where he implored voters to vote early.

"My guess is, if Ohio votes me in as president I'll be the next president of the United States," Romney said.