Democrats continue to claim that health care will help them mid-term. This time, they might be right.

There are two reasons why Democrats have called for a new approach to health care soon after the inauguration of President Barack Obama in 2009.

The first was obviously that health care costs continued to rise and thousands of Americans were forced to go bankrupt each year because of medical expenses. The idea was to find a way to provide more people with affordable health care coverage, and the approach they adopted was the Affordable Care Act. – soon known as Obamacare.

But then there was the second reason. By expanding coverage to a larger number of Americans, including expanding the availability of Medicare to the poorest Americans, Democrats have assumed there would be a political advantage. Providing affordable coverage would ensure that Republicans would seek to derive something of value from people, giving Democrats an integrated advantage.

Senate Minority Leader Charles E. Schumer (D-NY) said the benefit would come in the mid-term elections of 2010, just months after the law was signed.

"As people learn the law, it will be more and more popular," he said in March. "In November, those who voted for health care will find that an asset, those who voted against will find it a handicap."

This was not the case. A study showed that more than a dozen Democrats had lost their reelection because of their support for the Affordable Care Act.

Four years later, the majority leader in the Senate, Harry M. Reid (D-Nev.), Had made a similar prediction.

"I think it will be a net positive," he said of the bill, referring to the Senate races taking place. "I think so for the moment."

It was not Democrats lost control of the Senate, in part because of the awkward roll-out of the health registration website in late 2013.

This time, health care is becoming a winner for the party. Really.

Consider this announcement from Senator Joe Manchin III (D-W.Va.).

Manchin revisits an advertisement that he aired in 2012, in which he filmed a copy of the climate change legislation promoted by his party. It is his way of telling his constituents that he would put his priorities above those of his party, which was a majority in the Senate.

This year, it is working to reduce the coverage of pre-existing health conditions, a central part of Obamacare. In a race in West Virginia, a state that won Donald Trump by more than 40 points.

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

(Philip Bump / The Washington Post)

What happened? Well, on the one hand, Obamacare is newly popular, at least by Obamacare standards. After its adoption, it was generally perceived more negatively than positively, with this measure falling to a new low after the problems of the website in 2013. In the 2016 elections, however, it became more popular. Once Trump was elected and, importantly, once the Republicans began to revise the bill, this popularity has increased dramatically, according to polls from the Kaiser Family Foundation.

After Trump took office, the Democrats' advantage increased. The party now has a 17-point advantage, the widest margin since 2006.

(Philip Bump / The Washington Post)

In the meantime, other efforts by the administration to oppose ACA continue. For the first time since 2010, the percentage of Americans without health insurance remained stable in 2017. It was steadily declining. The Republican tax bill last December eliminated the individual mandate, jeopardizing the economic balance built into the bill.

The short explanation of why health care could help Democrats this year over 2010 and 2014 is simple: for the first time, the bill seems to have to be defended. Protecting things like people is usually a simple electoral winner.

Eight years later, Schumer may be right.