If U.S. Sen. Bill Cassidy is feeling some heat these days, well, he brought it on himself.

That's not intended as a criticism.

Cassidy, a gastroenterologist by trade who spent years treating uninsured patients in Louisiana's old Charity hospital system, ran for Senate as a staunch opponent of President Barack Obama's Affordable Care Act, as most of his fellow Republicans did.

When he ran for U.S. Senate in 2014, there was nothing Bill Cassidy talked about more than c…

But when the reality of one-party control of Washington hit, and the prospect of repeal became less a talking point and more a real possibility, he shifted gears, edged steadily away from the party line, and started focusing his energy on replacing the law with something that would fix its obvious problems but retain the many types of patient protections it's put in place.

And he's done it all in a remarkably public way.

Cassidy has introduced his own plan along with Susan Collins, a Maine senator and perhaps the chamber's most moderate Republican, that would allow states to keep Obamacare if they choose, and replace the individual mandate, which he philosophically opposes, with automatic enrollment with an opt-out provision.

Unlike many of his colleagues, he's acknowledged the severity of coverage losses from the House-passed bill that the Congressional Budget Office projected.

He's engaged with skeptical constituents at town hall meetings.

He's piggybacked on talk-show host Jimmy Kimmel's tear-jerking story about his newborn son's health challenges and promised that any law he supports would pass the "Jimmy Kimmel test" of protecting people with pre-existing conditions and banning lifetime coverage limits.

He's used President Donald Trump's campaign-trail promises to bolster his case, even as he's acknowledged that the Trump-backed House bill falls short of meeting them.

He's even reportedly reached out to Democratic senators in search of common ground.

In short, he's raised hopes that he'll fight against the type of coverage and protection rollbacks that are embedded in the hugely unpopular House bill, which is now in the hands of the Senate.

Of course, none of that will matter if Cassidy winds up backing something similar, as the bill GOP leaders are constructing behind closed doors reportedly is.

Majority Leader Mitch McConnell says he's determined to bring a bill to the Senate floor, perhaps this month, even though there have been no committee hearings on it and there seems to be no plan to let the public, or even Democratic senators, know what it says. McConnell appointed a 13-member working group to come up with a plan, and while he rightfully drew fire for choosing only men, he also made something of a statement by omitting Cassidy and Collins (Cassidy says he's been attending and participating in meetings anyway).

Former U.S. Sen. Mary Landrieu was not an automatic, knee-jerk vote for the Democratic Party…

But McConnell's walking a tightrope. Assuming all Democrats vote no, Republicans can only lose two of their own, and more senators than that have concerns. Some don't want to defund Planned Parenthood. Some are worried about reducing Medicaid spending and phasing out the expansion that has given many working poor people coverage, or about undermining coverage of pregnancy and substance abuse treatment. Some senators from closely divided states fear a "yes" vote will end their careers. And others think a bill crafted to ease those concerns won't be nearly conservative enough for their tastes.

Before the current debate, Cassidy wouldn't have landed on anyone's list of potential opponents. He's not a Planned Parenthood backer, he's criticized Medicaid expansion, and his seat is politically safe.

He's there because he put himself there, because he started talking about not just getting a win for the party, but protecting people.

And pretty soon, it seems, he'll have to decide just what that really means — and how much he's willing to compromise before the leadership can count on his vote.

Follow Stephanie Grace on Twitter, @stephgracela.