There were two reasons Democrats pushed for a new approach to health care shortly after President Barack Obama took office in 2009.

The first, obviously, was that health-care costs continued to increase and thousands of Americans were forced to declare bankruptcy each year because of medical costs. The idea was to figure out a way to offer more people affordable health-care coverage, and the approach they settled on was the Affordable Care Act — soon to become known as Obamacare.

But then there was the second reason. By extending coverage to more Americans, including by expanding the availability of Medicare to poorer Americans, the Democrats assumed that there would be a political benefit. Providing affordable coverage would position Republicans as seeking to take away something of value to people, giving the Democrats a built-in advantage.

Now-Senate Minority Leader Charles E. Schumer (D-N.Y.) figured that benefit would manifest itself in the 2010 midterm election, just months after the legislation was signed.

“As people learn about the bill, it’s going to be more and more popular,” he said that March. “By November, those who voted for health care will find it an asset, those who voted against it will find it a liability.”

That was not the case. One study figured that more than a dozen Democrats lost reelection bids because of their support for the Affordable Care Act.

Four years later, then-Senate Majority Leader Harry M. Reid (D-Nev.) made a similar prediction.

"I think for sure it will be a net positive,” he said of the bill, referring to Senate races that fall. “I think so by then for sure."

It wasn’t. Democrats lost control of the Senate, a function, in part, of the clumsy rollout of the health-care enrollment website in late 2013.

This time, though, health care is poised to be a winner for the party. Really.

Consider this ad from Sen. Joe Manchin III (D-W.Va.).

Sen. Joe Manchin III (D-W.Va.) has released a campaign ad criticizing opponent Patrick Morrisey's attempt to deny certain people health care. (Joe Manchin)

Manchin is revisiting an ad he ran in 2012, in which he shot at a copy of climate-change legislation promoted by his party. It was his way of telling voters in his state that he’d put their priorities over those of his party, which had a majority in the Senate.

This year, he’s taking aim at efforts to scale back coverage of preexisting health conditions, a central part of Obamacare. In a race in West Virginia, a state that went for Donald Trump by more than 40 points.

Manchin isn’t alone. According to an analysis by the Wesleyan Media Project, more than half of the ads promoting Democratic candidates at the federal level last month included a mention of health care. About a tenth of the time, the ads mentioned Obamacare specifically.

What happened? Well, for one thing, Obamacare is newly popular, at least by Obamacare standards. After it passed, it was generally more negatively viewed than positively, with that metric sinking to a new low after the website problems in 2013. During the 2016 election, though, it became more popular. Once Trump was elected and — importantly — once Republicans began floating possible overhauls of the bill, that popularity increased significantly, according to Kaiser Family Foundation polling.

Before the passage of the Affordable Care Act, Democrats were generally given a wide edge on the question of which party was better able to address health-care problems. After the bill passed, the two parties were briefly seen as equal in Fox News polling, with Democrats then holding a narrow edge.

After Trump took office, though, the Democratic advantage swelled. The party now has a 17-point advantage, the widest margin since 2006.

At the same time, Republicans aren’t making things easier for themselves. The Trump Justice Department in June offered its qualified support for a lawsuit brought by the state of Texas and a number of other Republican states that was aimed to block enforcement of the Affordable Care Act. (The lawsuit serves as the target in the Manchin ad.) During a court hearing last week, the government reportedly suggested that a ruling on the suit could wait until 2019, a timeline that would have obvious benefits in November.

In the meantime, though, the administration's other efforts to stand in the way of the ACA continue. For the first time since 2010, the percentage of Americans without health insurance held steady in 2017. It had been dropping consistently. The Republican tax bill last December eliminated the individual mandate, risking the economic balance built into the bill in the first place.

The short explanation for why health care might help the Democrats this year as opposed to 2010 and 2014 is a simple one: For the first time, the bill seems as though it needs to be defended. Protecting things people like is generally a straightforward electoral winner.

Eight years later, Schumer may be right.