Barack Obama’s promise to reform the US healthcare system played a big part in his campaign for the presidency. Voters responded warmly to the idea, and in principle still do: most continue to say they want the system changed. Yet barely half way through Mr Obama’s first year in office, his effort to keep his promise threatens to derail his administration.

The previous attempt at comprehensive reform failed spectacularly in 1994. Bill Clinton’s Democratic party then paid an awful price. The Republicans triumphed in that year’s mid-term elections. The setback transformed Mr Clinton’s presidency.

It was a memorable lesson, and suggests what might be at stake this time-yet few accused Mr Obama of innocence or recklessness when he vowed to revisit the issue. The climate of opinion had changed. Healthcare reform seemed more popular than ever. Interest groups once opposed to it recognised the new mood. Even before the debate began in earnest, they signalled willingness to surrender, as long as the terms were moderate.

Now, just months later, opposition to the administration’s approach is building inside Mr Obama’s own party. The Republicans, sensing a chance to force a crippling defeat on the new president, are ever more trenchantly opposed. Above all, independent voters are turning against the Democrats’ proposals. What has gone wrong? How, if at all, can Mr Obama revive his initiative?