By Nick Carey
MIDDLETOWN, Ohio (Reuters) - When Ohio voter Paul Presta opened his door to two election canvassers one recent Saturday he interrupted them in mid-sentence and asked Jim Lewis about an issue close to his heart.
"Do you support the second amendment?" he asked, referring to the U.S. constitutional right to bear arms, and pointed at Lewis.
Presta, 72, a semi-retired businessman, instantly relaxed, cheerfully telling them he had already voted for Republican presidential nominee Mitt Romney.
Lewis and his fellow activist Ann Becker are a new breed of canvassers going door to door along a sloping street full of modest and mostly well-kept homes in this declining steel town in Butler County. This is the first presidential election since the founding of the Tea Party movement which aims to reduce the size of U.S. government.
The two activists are not beholden to any campaign - some would say they are a rogue force - nor do they mention Republican presidential candidate Mitt Romney by name.
While they differ with former Massachusetts governor Romney on many policies and suspect his conservative credentials, they are working independently to help him win over undecided voters in swing states such as Ohio.
Fiercely opposed to the reelection of Democratic President Barack Obama, conservatives are trying to employ technology they used successfully earlier this year in a recall vote in Wisconsin to help Romney overcome Obama's narrow Ohio lead in the polls.
Conservative group American Majority Action trains volunteers such as Lewis and Becker to target "low-propensity" voters, or people who are not very interested in politics. They use Gravity, a mobile get-out-the-vote app that aims to filter out regular Republican voters and those who have already voted.
"I'm not doing this for Romney or the Republicans," said Chris Littleton, who is training some 50 volunteers to use the app. "I'm doing this because I'm against Obama."
Independent groups wandering around battleground states pose some risks for the Romney campaign. In the age of YouTube and Twitter, some officials worry that a canvasser could be caught on tape saying something too extreme for mainstream voters.
But asked about the Tea Party efforts, Romney spokeswoman Andrea Saul said: "Voters across the political spectrum are supporting Mitt Romney because they understand he is a leader who can deliver real change and a real recovery."
Among the voters Lewis and Becker encounter is Scott Whitt, 46, a truck driver who says upfront: "I'm undecided."
Friendly yet focused, they ask Whitt targeted questions about the U.S. debt, Obama's health reforms and the economy.
"Do you believe the government should take over health care?" Becker asks. "Are you better off now than in 2008?"
Whitt says government involvement in health care "doesn't sound good" and while he is "not doing badly" he worries about those without jobs.
After 10 minutes, Whitt is no longer undecided.
"I'm going to vote for Romney. He has the business experience we need," Whitt said.
American Majority Action said its volunteers at four Ohio field offices had called or spoken in person to 500,000 voters by this week as part of their get-out-the-vote drive.
This and other conservative groups such as FreedomWorks and Americans for Prosperity, which has backing from controversial oil and gas billionaire brothers Charles and David Koch, are targeting independent voters in Ohio and other key swing states.
Americans for Prosperity President Tim Phillips said his group expects to raise and spend $140 million nationwide by November 6.
Tea party activists point to a success in June, when Republicans said grassroots conservative efforts helped Wisconsin Governor Scott Walker survive a ferocious recall effort driven by labor unions.
No Republican has ever won the White House without carrying Ohio and Romney needs to mirror the presidential election of 2004, when Republican President George W. Bush's chief strategist Karl Rove engineered a narrow victory in the state by driving up turnout at the last minute.
To eke out an Ohio win in 2012, Romney needs to pile up big margins in Hamilton, Butler, Clermont and Warren counties in southwest Ohio around Cincinnati where American Majority Action's activists are working, plus other Republican areas.
Conservatives are employing the same tactics in other swing states. In Florida Debbie Wilson, a Tea Party activist and state director of FreedomWorks, says activists in her state have hit an average of 10,000 doors every weekend since mid-August, aided by volunteers driving in from neighboring conservative states.
In swing state Virginia, grassroots group We Are Virginia has opened seven field offices with backing from Middle Resolution, a small political action committee, and have partnered with American Majority Action. They are targeting about 60,000 undecided voters and independents.
Americans For Prosperity's Phillips says the group expects the volunteer activists it works with nationwide will make 10 million phone calls and knock on 3 million doors.
Focusing on Obama works because "some of these folks simply wouldn't show up for Romney," whom they deem insufficiently conservative, said Ned Ryun, president of American Majority Action's sister group American Majority.
"The Romney campaign shouldn't really worry about why folks are out there trying to fire the other guy," said Republican strategist Ford O'Connell. "His campaign should be happy to have all the help it can get."
(Additional reporting by Steve Holland; Editing by Greg McCune and Claudia Parsons)