Americans divide on the U.S. Supreme Court's ruling on the federal health care law and on Barack Obama's plans for the health care system alike, while favorable views of Mitt Romney's approach to health care fall shorter, with more undecided.

Just 30 percent in the latest ABC News/Washington Post poll have a favorable opinion of Romney's approach to health care, while 47 percent see it negatively, putting him underwater on the issue by a 17-point margin. Twenty-three percent are undecided, perhaps marking a lack of specifics by Romney on his plans - but giving him an opportunity to persuade.

See PDF with full results, charts and tables here.

The public at the same time divides by 45-48 percent, favorable-unfavorable, in views of Obama's plans for the health care system. On one hand that's clearly a weak score; on the other, it's 15 percentage points better than Romney's on the positive side, while essentially identical on the negative (with many fewer unsure, 7 percent).

There's a similar split on the high court's ruling last week: This poll, produced for ABC by Langer Research Associates, finds that 43 percent of Americans see the law favorably overall, 42 percent unfavorably. That's a closer division than existed on the law itself before the ruling - 36-52 percent, positive-negative, in an ABC/Post poll early last week. The difference is apparent disproportionately among Democrats.

A challenge for Romney, in addition to his weaker support overall, is the fact that critics of the Supreme Court ruling don't flock to him as an alternative. Among people who see the ruling unfavorably, Romney's plans for the system get a tepid 45-36 percent positive rating. Among those who see the ruling favorably, by contrast, 86 percent also see Obama's plans favorably.

PARTY and PARTISANS - Striking partisan differences exist, but with Romney's plans for health care earning weaker positive ratings among Republicans (62 percent) than Obama's among Democrats (80 percent).

Obama's plans for the system are 12 points more popular than Romney's among independents, the customary swing voters in national elections. But both men do poorly in this group - 38 percent positive for Obama, 26 percent for Romney. And Obama tips into majority negative territory among independents; 52 percent see his plans for health care unfavorably. Romney's at 46 percent negative, again with more undecided.

Romney, though, crosses into a majority negative rating among moderates (29-52 percent, favorable-unfavorable), while they divide about evenly on Obama's health care plans (48-44 percent). And conservatives see Romney's plans favorably by 12 points, while liberals see Obama's positively by 44.

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Views among groups on the Supreme Court's ruling are similar to views on Obama's plans for the system - a logical result in that the court upheld most of the law. In one difference, Democrats are 10 points less apt to see the ruling positively than to applaud Obama's efforts on the issue, with more undecided on the court's judgment.

OTHERS - There are some differences among other groups. Compared with non-graduates, college graduates express more positive views of the law and of Obama's plans for the care system, and more negative views of Romney's position on the issue. It's the same for young adults compared with seniors, and for racial minorities compared with whites.

As noted, there's an interesting comparison of pre-ruling attitudes on the law with views of the ruling itself. In late June, Democrats expressed favorable rather than unfavorable views of the law by 59-30 percent; today their views on the court's ruling are more broadly positive by 70-19 percent. Independents are no more positive on the ruling than they were on the law, but see the ruling less negatively than they saw the law itself, by a 9-point margin.

METHODOLOGY - This ABC News/Washington Post poll was conducted by landline and cell phone June 28-July 1, 2012, among a random national sample of 1,019 adults. Results have a margin of sampling error of 4 points. The survey was produced for ABC News by Langer Research Associates of New York, N.Y., with sampling, data collection and tabulation by SSRS/Social Science Research Solutions of Media, Pa.