WASHINGTON  For much of the year, Senator Hillary Rodham Clinton’s campaign has struggled to find a way to attack Senator Barack Obama.

Even for a campaign so adept at attacking, Mr. Obama proved a daunting target. He was extremely popular with Democrats, did not have an extensive voting record and, in fact, held many of the same views as Mrs. Clinton. The fact that he was African-American made the Clinton campaign wary  as happened more than once  that they would be accused of injecting racism into the campaign.

As much as anything, the Clinton campaign was concerned about launching an attack that could provide ammunition to Republicans should Mr. Obama become the party’s nominee. Bad enough that Mrs. Clinton should fail in her bid to become the second Clinton and first woman to be president. Worse if she should end up being blamed for the failure of Mr. Obama’s attempt to become the first African-American president.

But has the Clinton campaign crossed a line? Attacks that once seemed off-limits suddenly were pushed to the front of the stage. Embroiled in an increasingly tough fight and frustrated at Mr. Obama’s success and what the Clinton campaign claimed was coddling of him by the media, she began launching the very kind of attacks that will almost certainly be raised in a fall campaign should Mr. Obama win the nomination. She attacked his ethics and suggested that Mr. McCain would do a better job of protecting the country in a time of danger.