By Joan Biskupic, CNN legal analyst & Supreme Court biographer

(CNN) -- When a lawsuit challenging the Affordable Care Act reached his Washington, DC, appeals court in 2011, Judge Brett Kavanaugh was careful not to commit. He described the law requiring people to buy health insurance as "unprecedented" and the breadth of Obama administration's defense of it "jarring."

"[T]here seems no good reason," wrote Kavanaugh, now President Donald Trump's choice for the US Supreme Court, "that [the administration's] theory would not ultimately extend as well to mandatory purchases of retirement accounts, housing accounts, college savings accounts, disaster insurance, disability insurance, and life insurance, for example."

But at the same time, Kavanaugh said judges "should be wary of upending" Congress' effort to help provide Americans with quality health care. Kavanaugh would dissent from the 2-1 ruling in Obamacare's favor, but his legal reasoning was, in essence, a dodge. He said judges simply had no jurisdiction at that point to resolve the merits of the dispute.

Kavanaugh has never outright rejected, or endorsed, the 2010 law known as Obamacare. His opinions bear the mark of a careful jurist on a court well known as a launching pad to the Supreme Court. He watched what he said.

Now, as health care promises to become a flashpoint in his Senate confirmation battle, Kavanaugh may have to persuade crucial middle-ground senators, such as West Virginia Democratic Sen. Joe Manchin, that he would preserve Obamacare, particularly its protections for people suffering from cancer, diabetes and other so-called pre-existing conditions.

Manchin is scheduled to meet with Kavanaugh on Monday, becoming the first Democratic senator to do so. Manchin, running for re-election in conservative West Virginia, could be under heavy pressure to support Kavanaugh this fall.

The fate of the health care law isn't an abstract question. The Trump administration is backing a lawsuit brought by Texas and other Republican-led states challenging the requirements that insurers offer coverage to everyone regardless of their medical history and do not charge more to people who have had certain health conditions.

Manchin this month urged Attorney General Jeff Sessions to reconsider the administration's refusal to defend the law, which protects millions of Americans, including, Manchin said, nearly 800,000 West Virginians living with pre-existing conditions.

That new case, Texas v. United States, could ultimately land at the Supreme Court, where a new Justice Kavanaugh, tapped to succeed the retiring Anthony Kennedy, could make the difference in whether a popular ACA plank survives. (Kennedy voted against the individual insurance mandate in 2012, but supported Obamacare in a separate 2015 test; it is difficult to predict how Supreme Court votes would fall in the new Republican challenge, but they are likely to be narrowly divided.)

Kavanaugh's critics on the left contend his conservatism over the past 12 years on the US Court of Appeals for the District of Columbia Circuit would lead him to rule against the Affordable Care Act.

Signs of his opposition to the law were plainly sufficient to satisfy Trump, who has long railed against the signature domestic achievement of President Barack Obama and has vowed to appoint justices who would overturn it.

But before he was nominated by Trump earlier this month, it was conservatives who expressed concerns. Some advocates on the right, perhaps jockeying for their other candidates on Trump's list of prospective nominees, argued that Kavanaugh had not demonstrated sufficient hostility to Obamacare -- a regular litmus test for Republican politicians.

In fact, Kavanaugh's record indicates skepticism for the multifaceted law but not surefire rejection. The one area where a clear record exists involves the law's birth control mandate. He wrote a 2015 opinion that would make it easier for religious organizations to win an exemption from the mandate that employers provide contraceptive insurance coverage. He said the paperwork requirement for an exemption encroached on the free exercise of religion.

2011 ruling

When a DC Circuit panel upheld the law in 2011, Kavanaugh dissented, not on its constitutional merits, but on procedural grounds.

He said it was premature to resolve a dispute that involved an insurance mandate to be imposed in 2014, with a tax penalty the following year.

"Some have said that the health insurance industry prefers a decision now and that Congress would have wanted courts to accommodate that concern," he wrote in the 2011 case of Seven-Sky v. Holder. But Congress did not make that clear and "there is no 'early-bird special' exception."

Yet as he dissented, Kavanaugh laid out limits on Congress' power under the Constitution's Commerce Clause. The crux of the litigation at that point was whether Congress had the power to order people to buy a product.

After the Supreme Court had ruled on the law, Kavanaugh spoke approvingly of a portion of the high court's 2012 decision finding that the law violated Congress' power to regulate interstate commerce. "The power to regulate commerce is not the power to force people to enter commerce," Kavanaugh said at a November 2012 Federalist Society meeting.

The high court in its June 2012 ruling, however, upheld the law in a controversial, bitterly fought opinion by Chief Justice John Roberts, based on Congress' taxing power. Kavanaugh declined to comment much on that compromise beyond the observation that Roberts was seeking "to defuse an otherwise hot constitutional issue."

Another technical decision

In 2015, Kavanaugh similarly dissented on technical grounds when the full DC Circuit refused to take up a challenge to the law based on a claim that it was a revenue-raising measure that improperly began in the Senate, not the House of Representatives. That case tested the Constitution's Origination Clause.

A panel of the DC Circuit had earlier ruled that the Affordable Care Act need not have begun in the House because it was not a revenue-raising bill.

Kavanaugh said he wanted a new hearing to fully air the issue. In a lengthy dissent in Sissel v. Department of Health and Human Services, Kavanaugh unspooled his interpretation of Origination Clause history. He also contended the law was a revenue-raising bill because it imposed taxes to raise revenue. But in the end, he rejected the challengers' claim because a version of the legislation had begun in the House in October 2009.

"To read my opinion so far, you might wonder whether I think the world will end not in fire, or in ice ... but in an Origination Clause violation," he wrote at the end of his opinion, picking up on a quip from a Supreme Court ruling in an unrelated, but similarly dry and esoteric, case. "I of course realize there are more important constitutional issues. This case is not Marbury v. Madison redux. But the case is still quite important."

Contraceptive mandate

Kavanaugh was also in dissent in the 2015 case Priests for Life v. Department of Health and Human Services, focused on the religious exemption to the Affordable Care Act.

He dissented when the DC Circuit declined full court review of a religious group's objection to the process for employers seeking to opt out of the contraceptive mandate.

Priests for Life challenged the procedure for certifying eligibility for exemptions and avoiding fines, contending the paperwork involved burdened religious rights. Kavanaugh agreed, saying, "To plaintiffs, the act of submitting this form would, in their religious judgment, impermissibly facilitate delivery of contraceptive and abortifacient coverage."

He said judges should not question the sincerity of their beliefs or grounds for feeling complicit in the birth control they find immoral.

When the Priests for Life case made it to the Supreme Court, with other religious groups' claims, the following year, the justices threw out the DC Circuit's opinion.

In a short unsigned decision, the high court urged the government and religious nonprofits to compromise on a process that would allow the groups to bypass the form but guarantee that insurance companies, working with the government, continued to provide contraceptive coverage to the religious entities' employees.