Democratic Senator Kay Hagan is one of the most vulnerable Dems in the country, and her problems are said to be largely about Obamacare, thanks to the millions of dollars Americans for Prosperity has spent on ads attacking her over the law.

So it’s curious that Hagan today made an aggressive case for a major pillar of the law that’s supposedly on the verge of ending her Senatorial career: The Medicaid expansion.

Or, at least, it’s curious if you haven’t been paying attention, and aren’t aware that multiple Dems — even vulnerable ones — have been making a strong case for the expansion, and using it to draw a contrast with GOP opponents, even if Obamacare is not the centerpiece of their campaigns.

This Hagan moment was key. It came during a hearing today for Sylvia Matthews Burwell, Obama’s pick to head the HHS, and Dylan Scott has the details:

“Last year in North Carolina, our state legislature and governor decided against expanding the state’s Medicaid program,” Hagan said as she started her questioning, “and as a result, about 500,000 people who would have qualified for coverage through Medicaid are not now able to do so.”

“These are some of the most vulnerable in our society,” she said, “who will continue to seek care in emergency rooms and then will leave chronic conditions unmanaged, which we know is detrimental to their health and the economy.” […]

Hagan then gave the example of a 35-year-old single woman whose income is below the federal poverty level — therefore falling in the Medicaid expansion gap, which in non-expanding states means that those Americans will not have access to health coverage under Obamacare.

“So if a state had expanded it, she would have had access,” Hagan said, “where in the 24 states that haven’t expanded it, there is this huge number of people, in my state, 500,000, that are still without coverage.”

The key context here: Hagan’s new opponent, state House speaker Thom Tillis, was a staunch opponent of Obamacare’s Medicaid expansion, which would have expanded coverage to half a million North Carolinians. During the GOP primary he even ran an ad boasting that he was solely responsible for stopping that outcome “cold.”

It’s widely understood that Tillis’ role in steering the state in a sharply conservative direction on issues such as voter ID, abortion, and the safety net means this race will showcase one of the sharpest ideological contrasts of any contest in the country. Less well understood is that Dems will make the Medicaid expansion a part of that contrast — it will be part of the case that Tillis’ agenda and ideology are terrible for working and middle class Americans.

Once again: Dems are already using the Medicaid expansion as an issue, to varying degrees, in multiple Senate races. In Louisiana, Mary Landrieu has made a strong moral and economic case for the Medicaid expansion, claiming Obamacare’s benefits are “worth fighting for” and that her Republican foe’s repeal stance will put him at a “distinct disadvantage.”

In Michigan, Dem Gary Peters has offered a moral case for Obamacare and attacked Republican Terri Land over repeal, challenging her to take a position on the expansion there. Land refuses to say where she stands. Other Republicans have struggled with this issue. In Arkansas, GOP candidate Tom Cotton has refused to take a position on his state’s version of the expansion. Today’s Arkansas Times has a good piece detailing the ways it’s already helping people, another reminder that the politics here are dicey.

Meanwhile, the hapless Scott Brown — whose main rationale for running for Senate is that Obamacare sucks — is still pulling a homina homina homina on the expansion in New Hampshire. From today’s Boston Globe, which nails the larger dynamic:

He did not directly answer questions from a reporter about whether he supported or opposed the Medicaid expansion….Brown’s conundrum is emblematic of a tension facing Republicans around the country. The health law’s low standing in opinion polls is a key reason many political handicappers are predicting that Republicans will regain control of the Senate after this November’s congressional elections.

But Democrats are hoping to at least mitigate some of that damage, and possibly even win advantage, by forcing Republican critics to take positions on the law’s more popular provisions, including the Medicaid coverage expansion that was made optional in a Supreme Court ruling.

In all these places, Obamacare is supposed to be toxic — nothing but a huge loser for Dems and political gold for Republicans. Surely the law is a net negative for Dems, but it’s finally sinking in more broadly that the politics of Obamacare are complicated. Indeed, as the First Read crew suggests today, with Republicans suffering a buffoonish setback on premium payment rates, it’s possible the GOP’s increased emphasis on #Benghazi is partly due to a recognition that the ACA is not shaping up as the certain long-term winner for them that they anticipated.

Read more: 

Paul Waldman: The five stages of GOP scandal-mongering

Greg Sargent: The GOP gives up on fixing its Latino problem

Dana Milbank: Republicans’ Benghazi show trial


GALLERY: Rachel Maddow picks the next Democratic leaders