Joe Biden is taking an aggressive approach to defending Obamacare, challenging not just President Donald Trump but also some of his rivals for the Democratic presidential nomination who want to replace the current insurance system with a fully government-run model.

The former vice president will spend much of the coming week talking about his approach to health care, including remarks he’ll deliver on Monday in Iowa at a presidential forum sponsored by AARP. His almost singular focus on the 2010 health care law has been on display recently in the early voting states.

In Iowa, he declared himself “against any Republican (and) any Democrat who wants to scrap” Obamacare. Later in New Hampshire, he said “we should not be scrapping Obamacare, we should be building on it,” a reference to his approach to add a government insurance plan known as the public option to existing exchanges that sell private insurance.

Biden is hoping his positioning as Obamacare’s chief defender could be helpful on several fronts. It’s a reminder of his close work alongside President Barack Obama, who remains popular among Democratic voters. And it could reinforce his pitch as a sensible centrist promising to rise above the strident cacophony of Trump and Democrats including Sens. Bernie Sanders, Elizabeth Warren and Kamala Harris, all single-payer advocates.

Perhaps as important, it’s an opportunity for Biden to go on offense ahead of the next presidential debate at the end of July. Biden has spent the past several weeks on defense, reversing his position on taxpayer funding for abortions and highlighting his past work with segregationist senators. Harris slammed him during the first debate, blasting the segregationist comment and criticizing his opposition to federal busing orders to desegregate public schools during the same era.

Each of the episodes raised questions about whether Biden can maintain his front-runner status.

In New Hampshire over the weekend, it was clear Biden wanted to turn the tables as he touted the idea of a “Medicare-like” plan that any American could buy as opposed to a “Medicare-for-all” that would be imposed on everyone.

“I think one of the most significant things we’ve done in our administration is pass the Affordable Care Act,” Biden said. “I don’t know why we’d get rid of what in fact was working and move to something totally new. And so, there are differences.”

He argued that some of his opponents, with the exception of Sanders, aren’t fairly representing the consequences of their proposals.

“Bernie’s been very honest about it,” Biden said. “He said you’re going to have to raise taxes on the middle class. He said it’s going to end all private insurance. I mean, he’s been straightforward about it. And he’s making his case.”

Asked specifically whether Harris has been honest about how her plan would affect private insurance, Biden said, “I’ll let you guys make that judgment.”

During last month’s debates, Harris, Warren and Sanders raised their hands when candidates were asked as a group whether they supported eliminating private insurance. A day later, Harris, a Senate co-sponsor of Sanders’ single-payer bill, reversed her answer — the second time since her campaign launch that she’d walked back her seeming endorsement of eliminating private insurance.

She explained that she interpreted the debate moderator’s question as asking whether she’d be willing to give up her existing coverage as part of a single-payer model. She said she wants private policies to remain “supplemental” options for consumers.

Sanders, meanwhile, hit back at Biden, clarifying that his plan would be a net financial benefit for most households: Their federal taxes would go up, but their private insurance premiums, deductibles and co-pays would be eliminated.

“At a time when Donald Trump and the health insurance industry are lying every day about ‘Medicare for All,’ I would hope that my fellow Democrats would not resort to misinformation about my legislation,” Sanders said in a statement responding to Biden’s New Hampshire comments.

Biden hasn’t yet introduced his full health care plan, but has said it will be anchored by a “Medicare-like” plan that would be available to anyone — including the 150 million-plus Americans now covered by job-based insurance, a group now ineligible for exchange-based policies. Biden has indicated that income-based subsidies would ensure that any household could get coverage. The idea is to expand coverage immediately and shake up insurance markets long-term by forcing private insurers to compete alongside the government, theoretically pressuring to lower their premiums and out-of-pocket costs for private policy holders.

Biden isn’t the only public-option advocate running for president.

Former Colorado Gov. John Hickenlooper warns that Republicans will brand single-payer as “socialism,” hurting Democrats in the general election. Colorado Sen. Michael Bennet echoes Biden’s argument with a call to “finish the work we started with Obamacare.”

Minnesota Sen. Amy Klobuchar touts a public option as the next logical move even for single-payer advocates.

“I think it is a beginning and the way you start and the way you move to universal health care,” she said in the first debate.

If anything, the dynamics illustrate Democrats’ overall leftward shift on health care.

A decade ago, as Obama pushed for ACA, the public option was effectively the left-flank for Democrats, a reality made obvious when Obama angered House liberals by jettisoning the provision to mollify some moderate Senate Democrats needed to pass the legislation. Now, after Sanders’ insurgent 2016 presidential bid and his promise of “health care as a human right,” the left has embraced single-payer, with moderates moving to the public option.

Yet with the exception of Biden, the moderates are languishing far back in polls, leaving the former vice president to capitalize on the dividing lines and promising that he would do what Obama couldn’t.

“And,” he declared, “it can be done quickly.”