Mitt Romney wrapped the most important speech of his life, for Thursday night’s session of his convention, around an extraordinary reinvention of history — that his party rallied behind President Obama when he won in 2008, hoping that he would succeed. “That president was not the choice of our party,” he said. “We are a good and generous people who are united by so much more than divides us.”

The truth, rarely heard this week in Tampa, Fla., is that the Republicans charted a course of denial and obstruction from the day Mr. Obama was inaugurated, determined to deny him a second term by denying him any achievement, no matter the cost to the economy or American security — even if it meant holding the nation’s credit rating hostage to a narrow partisan agenda.

Mr. Romney’s big speech, delivered in a treacly tone with a strange misty smile on his face suggesting he was always about to burst into tears, was of a piece with the rest of the convention. Republicans have offered precious little of substance but a lot of bromides (“A free world is a more peaceful world!”) meant to convey profundity and take passive-aggressive digs at President Obama. But no subjects have received less attention, or been treated with less honesty, than foreign affairs and national security — and Mr. Romney’s banal speech was no exception.

It’s easy to understand why the Republicans have steered clear of these areas. While President Obama is vulnerable on some domestic issues, the Republicans have no purchase on foreign and security policy. In a television interview on Wednesday, Condoleezza Rice, the former secretary of state, could not name an area in which Mr. Obama had failed on foreign policy.