By Eric M. Johnson

CINCINNATI, Nov 5 (Reuters) - After all the fundraising, political ads, rallies, meetings and get-out-the vote efforts, a few counties in just one state - Ohio - could have an outsized say in the outcome of Tuesday’s presidential election.

At a national level polls show President Barack Obama and Republican rival Mitt Romney tied. Under most calculations, Ohio is currently the most critical battleground in the candidates’ state-by-state race to capture the 270 electoral votes needed to win the White House.

A Reuters/Ipsos poll on Sunday showed Obama leading the former Massachusetts governor 48 percent to 44 percent in Ohio. Other polls show a similar tight race in the Midwestern state of 11.5 million people. Obama won the state by 4.6 percentage points in his defeat of Republican John McCain in 2008.

Here is what election analysts say the campaigns need to do to win longtime swing state Ohio and its 18 electoral college votes.

- The Obama team must maximize turnout in the north, particularly in Cuyahoga County around the industrial and manufacturing Democratic stronghold of Cleveland, an area that is home to roughly 10 percent of the state’s population. The northern part of the state is deeply tethered to the auto industry and has a strong presence of organized labor.

- Obama needs to avoid losing badly in Hamilton County, which the Democrat won in 2008 but which typically leans Republican. Hamilton County is in the southwestern corner of the state, adjacent to Kentucky and includes the city of Cincinnati. It has many socially conservative voters - and is surrounded by some of the most Republican-friendly parts of Ohio, including House of Representatives Speaker John Boehner’s 8th District. Obama is fighting for a draw there, said a Democrat with ties to the campaign. “But we can’t lose by more than 3 to 4 points.”

- The Romney campaign needs to maximize turnout in the suburban and rural areas, especially in the conservative southeast and in Hamilton County, and to eat into Obama’s margin in the north. Romney likely needs to carry Hamilton County to have a shot at the state overall.

- Traditionally moderate Franklin County in the central part of the state, anchored by Ohio’s largest city, Columbus, could prove decisive if both campaigns get their voters out in force. Columbus, the state capital, leans Democratic, although its suburban outskirts lean Republican.

- Also prized are Stark County, which straddles the Democrat-heavy northeast and the conservative southeast and has been on the side of the winner in 10 of the previous dozen presidential elections, and Montgomery County, home to a large Air Force base and the small city of Dayton. Romney has said Obama’s planned defense budget cuts would hurt the area.

GROUND EFFORTS CRUCIAL

The battle for Ohio will likely be decided by each campaign’s efforts on the ground. An Obama campaign spokeswoman said thousands of volunteers worked on its behalf over the weekend in Ohio; the Romney campaign said roughly 15,000 worked for it on Sunday.

If both campaigns maximize turnout, everything could hinge on the decisions of uncommitted voters, many of whom will be influenced by personal connections.

“Families and then friends influence people more than every other combination of TV ads, the news media and organizational affiliation,” Ohio Democratic strategist Greg Haas said. “They are in the same boat.”

Alexa Marinos’ family, which owns an ailing dry-cleaning business, pushed her into Romney’s column even after she had donated cash to Obama, with whom she agrees over support of same-sex marriage.

“I feel more confident in Romney being able to guide us out of this recession,” said Marinos, of liberal Cleveland.

Obama canvasser Jack Frase, plying for votes recently in Cincinnati, was able to use Obama’s positions on women’s issues to convince 44-year-old Janette Gregory, who was previously undecided, to back Obama.