Voters here have heavily supported Republican presidential candidates for close to 50 years, but local party officials said every potential vote will be sought for the November election.

Local party officials from both sides said they are gearing up for a protracted battle and independent voters will be the prize possession.

Southwest Ohio is viewed by pundits as a critical area to winning Ohio, which in turn is considered a critical “swing state” in winning the presidential election.

For the first time, a Democratic presidential candidate has opened an office separate from the party’s office this year in Butler and Warren counties. The Obama campaign has opened offices in Middletown and Mason.

“If you look at the scenarios for Romney winning, Ohio plays into almost all of them,” said Bryan Marshall, a professor of political science at Miami University in Oxford. “There’s going to be a lot of money from both political parties and third party groups spent here and I would think a lot of visits to the area by both candidates.”

Although the Republican candidate has garnered 60 percent to 70 percent of the vote in Warren and Butler counties in the last three presidential elections, and the last time a Democrat won in either county was in 1964, representatives said getting voter turnout for their side will be important.

For Republicans, Butler and Warren counties are a base in which to offset the more liberal-leaning northeast Ohio. For Democrats, it’s a chance to steal away those votes and turn Ohio into a blue state.

Marshall said no Republican had ever won a presidential race without winning Ohio.

“Everyone in Southwest Ohio is fully cognizant in how important this area is, particularly for Republican candidates,” said David Kern, head of the Butler County Republican Party.

“Butler County has a large number of Democrats and a large number of independents,” said Kathy Wyenandt, head of the Butler County Democratic Central Committee. “It’s probably not an expectation that Obama will win (in Butler County), but we can move the meter by a few percentage points and that could turn out to be critical to winning the state.”

Bethe Goldenfield, head of the Warren County Democratic party, noted that the Democratic presidential candidate gained nearly 4 percent in votes from 2008 over 2004 results, and she is hoping to improve that upward trend.

“Even though I know we won’t get the majority, our goal is to hold the line and hopefully increase the percentages from what they were four years ago,” Goldenfield said.

Both sides claim they are gaining momentum in the race and are already sending out supporters to canvas the area with literature and phone calls.

“I’ve never seen fire in the belly like I’ve seen this year,” Kern said. “People are disgusted by the incompetence of the president and his attempt to take the republic away from the people of the country.”

Goldenfield, however, said the Democratic Party gained momentum in its efforts to repeal the union-busting Senate Bill 5 in 2011.

“Senate Bill 5 and Governor Kasich’s attack on the middle class created a lot of fertile ground, and we gained a lot of independent voters who I believe are going to stick with the Democrats in the election cycle,” Goldenfield said.

Kern does not believe that momentum will hold.

“I know a lot of people in unions who opposed SB5, but they also are against what the president is doing,” Kern said.

Neither side can really claim much victory in Ohio at this point, Marshall said.

“There is an argument Democrats have gained momentum, but the latest polling still shows Obama and Romney neck and neck,” Marshall said.

Another factor that could play a role is if Romney picks Sen. Rob Portman as his vice president. Portman has strong ties to Southwest Ohio, with his family owning Lebanon’s Golden Lamb restaurant.

“I think the focus will be on the president, not the vice president,” Kern said. “I believe Senator Portman would be an excellent running mate, but the focus will ultimately be on the president.”

The area is also important for the Senate race between Democratic Sen. Sherrod Brown and his Republican opponent, state treasurer Josh Mandel. “That is a crucial race for Republicans who are trying to gain control of the Senate,” Marshall said. “The money spent here by the Romney campaign will also in a way be money for Mandel. It’s a two-for-one sort of situation.”

Butler County wasn’t always a Republican stronghold, according to Butler County historian Jim Blount. The first Republican presidential candidate to win Butler County was Calvin Coolidge in 1924. The county supported Democratic President Franklin D. Roosevelt in each of his four victories in the 1930s and ’40s, Blount said. The last Democrat to win Butler County was Lyndon Johnson in 1964. Johnson was the only Democrat presidential candidate ever to win in Warren County, according to historian John Zimkus.

Contact this reporter at (513) 696-4544 or jmcclelland@coxohio.com.