By Jessica Wehrman & Jack Torry

Former Ohio Gov. Ted Strickland will seek to challenge Republican Sen. Rob Portman next year, launching what could become one of the top-tier Senate races of 2016.

Strickland, who has been talking to donors and supporters in recent weeks, announced his decision to run in an email to supporters this morning.

"I'm running for the United States Senate in 2016 because I am determined to restore the American Dream for working people in this country," Strickland said, adding that he believes in the American Dream because "I've lived it."

Strickland is the eighth of nine children in his family and the first in his family to go to college.

"I know how difficult it is to move up in this world, and the deck is increasingly stacked against working people," he said.

Reaction from Portman's camp was swift.

Portman, in a statement, said he "welcomed" Strickland "back to Ohio."

He said he looked "forward to a candid exchange of ideas during this critical time for so many in our state."

"The coming months will give Ohioans an opportunity to contrast my vision for a better future for Ohio workers with his past tenure as governor when hundreds of thousands of jobs disappeared from our state," he said.

Portman campaign manager Corry Bliss sent an email to Portman supporters announcing the launch of a website devoted to attacking Strickland's record as governor.

"Remember Ted Strickland?" Bliss wrote. "He was denied re-election as governor after hundreds of thousands of Ohio jobs disappeared during his term in office."

Strickland is the second Democrat to enter the race against Portman, who is serving his first term in the U.S. Senate. Cincinnati Councilman P.G. Sittenfeld, a Democrat, announced his plans to run for Senate in January, and was in Washington earlier this month for a fundraiser featuring former White House spokesman Mike McCurry, former deputy White House Press Secretary Bill Burton and former Clinton White House speechwriter Laura Capps. Sittenfeld's campaign has reportedly raised about $500,000 so far.

Asked to comment on Strickland's impending announcement, a spokesman for Sittenfeld referred a reporter to a prior quote from Sittenfeld's campaign manager, Ramsey Reid, saying the Sittenfeld " admires Ted Strickland but is focused on his own campaign."

Portman launched his campaign by releasing a list of 500 elected Ohio GOP officeholders who had endorsed him. He later added 5,000 other endorsements from Republican grassroots across the state.

He has more than $5.8 million in the bank.

Curt Steiner, who managed Portman's first House race in 1993 and has advised a wide variety of GOP candidates, said that Portman has a strong network of financial donors in Ohio and across the country and predicted "he will out-raise the Strickland campaign."

Portman, a former southwest seven-term Ohio congressman, who served as the U.S. Trade Ambassador and later Director of the Office of Management and Budget in the George W. Bush White House, won in 2010 with 57 percent of the vote, but Democrats are hopeful that his re-election bid during a presidential election year could give them a boost.

Jennifer Duffy, who monitors U.S. Senate races for the nonpartisan Cook Political Report, said that the race "could go either way."

"I don't think we know yet," she said. "We know that there's going to be a primary. We do know that Portman's going to run a great, strong campaign. What we don't know is what the political environment is or who's going to be at the top of the ticket in the presidential races."

Strickland's announcement comes a little over a week after he left his position leading the political arm of the progressive Center for America Progress in Washington, D.C.

He has spent the last few weeks contacting supporters and donors, and has assembled a team of key consultants, including Willard, Aaron Pickrell, who led both of Strickland's campaigns for governor and who helped President Barack Obama win Ohio in 2008 and 2012 and John Haseley, who served as Strickland's chief of staff when he was governor.

Strickland won the governor's race in 2006 but lost re-election four years later to Republican Gov. John Kasich by 2 percentage points.

He made it clear his race would focus on the middle class.

"To save the American Dream, we need to go back to the basics," he said "We need to create living-wage jobs and invest in the kind of infrastructure projects that benefit our communities. We need to make college more accessible and affordable so that our young people can get an education, get a job, and start saving to buy a home, support their families and retire with a sense of dignity and security. We need to make smart choices on fair trade that reward the worker instead of the wealthy.

"If we do this, we can put our country back on the right path and bring opportunity for all.

(c)2015 The Columbus Dispatch (Columbus, Ohio)