(AP Photo/Elise Amendola)DES MOINES, IA – The leading Democrats vying for their party's presidential nomination clashed over the critical issue of health care while offering starkly contrasting visions for the nation's ideological direction before thousands of cheering Iowa activists at a raucous event kicking off the three-month sprint to the first-in-the-nation caucuses. Biden said he would overhaul health care nationwide without "increases in taxes for the middle class. The former vice president has promised not to "abandon" Obama's signature health care law. The 37-year-old also offered a veiled swipe at Warren, Biden and Sanders — all in their 70s — by chiding candidates for being content to "wait for action." Warren supporters erected a giant likeness of Bailey, the senator's golden retriever.

Warren says that, far from having boxed herself in politically, she's been working on her health care plan for months and still sees it as a winning issue. "You're going to get health care with no premiums, no deductibles, no fear of bankruptcy if you have a health emergency." Sara Collins, vice president for coverage and access with the nonpartisan Commonwealth Club, said the key involves changing how the health care tab is divided up among employers, government and individuals. Unlike Warren, Sanders has already released payment options, including higher taxes on wealthy Americans and an employee payroll tax of 7.5%. But that would give federal authorities more control over employee health costs than employers, potentially affecting jobs.