Even on one of their most frequently debated policies, Obama once said: "Ninety-five percent of our health care plan is similar."
Stephen Hess, a presidential scholar at the Brookings Institution, said their policy agreements ironically have added to the tension in their campaign.
"There is simply no doubt that when two candidates virtually agree, you have to find other reasons to find an argument about why you should be for one rather than the other," he said. "That's why suddenly the issues in this campaign are issues of character rather than position. And once they are issues of character, they can get very personal."
Both want to provide health care for all and end the Iraq war. They want to increase tax credits for college tuition, protect abortion rights and renegotiate the North American Free Trade Agreement to strengthen labor and environmental standards.
They want to reform immigration in largely the same way and both have energy plans that would cost $150 billion over 10 years.
Here are some of the most significant points of contention that may help voters in the 10 contests choose between Clinton and Obama.
HEALTH CARE Both say they have a goal of providing universal coverage and will try to lower costs to make it more affordable. The biggest difference is that Clinton would require everyone to get health insurance while Obama would not. Clinton says her plan is the only one that is truly universal because people won't get coverage unless they are required to, similar to auto insurance. Obama says people will get insurance only if they can afford it.
HOUSING Both want to help homeowners facing foreclosure, but Clinton's plan includes a five-year freeze on interest rates for all subprime mortgages, which often go to borrowers with the poorest credit. Obama disagrees with the proposed freeze, saying it will drive up interest rates and keep other people from getting mortgages.
Both candidates also support legislation to help homeowners with "underwater mortgages" - meaning their homes are worth less than the mortgage. That legislation would provide government guarantees for their mortgages, but Clinton wants to go one step further than Obama. She wants the federal government to buy underwater mortgages and reduce payments to a level homeowners can afford.
EDUCATION Obama has called for something that irks teachers' unions. He says educators should be rewarded based on performance as long as test scores aren't the sole measure. Clinton says she would support merit pay, as long as it was based on school-wide performance and not the individual teacher.
At the college level, both want to provide more tuition relief through tax credits - up to $3,500 for Clinton and $4,000 for Obama. Obama also would require something Clinton does not. Students would have to perform 100 hours of community service to qualify each year.
RETIREMENT Both candidates say they would help low- and middle-income workers set up personal retirement accounts and provide government matches for the first $1,000 saved annually. But they would go about it differently.
Clinton would match 100 percent for families earning $60,000 or less, with smaller breaks for those earning up to $100,000. Obama would match 50 percent of the first $1,000 for families making less than $75,000.
On Social Security, Clinton has refused to say publicly what options she would consider to keep the system afloat long term. Obama has said the best choice is to raise Social Security taxes on people earning more than $200,000.
FOREIGN POLICY The debate over whether the president should directly negotiate with rogue leaders has been one of the most prominent issue differences in the campaign. Obama says he would meet with heads of state in places like Cuba, Iran and North Korea. Clinton says those meetings could be used for propaganda and her first response will be outreach through other diplomatic channels.
IMMIGRATION Another much-discussed division: whether to give driver's licenses to illegal immigrants. Obama says yes, for safety reasons. Clinton says no.
TAXES Both candidates would repeal Bush's tax cuts on wealthy Americans to pay for their programs. Obama also has a plan for across-the-board tax cuts for most workers. Clinton doesn't support Obama's plan because of it $80 billion cost and because it would apply to families with significant incomes. Obama's campaign says it would begin a phase-out for households that earn around $150,000.
