Many constitutional issues never come before the Supreme Court, which only rules on lawsuits. The Justice Department's Office of Legal Counsel issues rulings based on the Constitution, which are generally regarded as binding precedents by administrations of different parties, even though cases never go to court.
Presidents of different parties regularly issue signing statements, saying that they will not carry out provisions of laws they sign that they regard as unconstitutional. Barack Obama decried signing statements when he was campaigning, but as president he has issued them himself.
Members of Congress may reasonably regard themselves as bound to vote against measures they conscientiously believe unconstitutional. Barry Goldwater did this when he voted against the Civil Rights Act of 1964, even though he had integrated his own business many years before, on constitutional grounds.
Goldwater's constitutional argument, predictably, wasn't accepted by the Supreme Court. And his vote gave the Republican Party an unfair reputation for being anti-civil rights. But I think he was entitled to think his oath required him to vote that way.
Clearly the two parties are divided on the constitutionality of the Obamacare mandate. Polls have shown large majorities of voters think the provision is unconstitutional, though one can wonder whether many have given the matter much thought.
But they're certainly giving it more thought after this week and will likely give it more when the decision comes down.
Voters can reasonably ask candidates for Congress their views on this and other constitutional issues and call on them to vote against measures they consider beyond Congress' constitutional powers.
If the Court overturns Obamacare, Obama may be tempted to attack the court. He should beware. In 1937, Franklin Roosevelt, a few months after landslide re-election, proposed to pack the Supreme Court with new appointees.
Gallup polls showed majorities opposed, and in the next election, proponents of FDR's New Deal lost their congressional majorities. Lesson: Most American voters worry about the Constitution.