WASHINGTON — Five years ago, lawmakers stood side by side on the steps of the Capitol and belted out an impromptu rendition of “God Bless America” after the terrorist attacks.

Democrats and Republicans pulled together, as did the country at large. “We had an astonishing moment of unity,” President Clinton said yesterday.

But now, the two political parties could not be further apart. On the fifth anniversary of the attacks, Democrats and Republicans struggled for the upper hand on what has become the main issue of the midterm campaigns — the war in Iraq and its relationship with the broader battle against terrorism.

Both sides insist they are not politicizing the anniversary. And numerous commemorative events were held at which political harmony was emphasized. Lawmakers even planned an encore session on the Capitol steps.

But then things got back to business as usual. With control of the House and Senate hanging in the balance, the political rhetoric from the two parties is often 180 degrees apart.

Republicans assert that President Bush’s leadership has made the nation safer from terrorist attack. Democrats argue America is less safe. They accuse Republicans of failed policies that have cost thousands of American lives, and they depict Iraq as a diversion from the war on terror — not the main front that Mr. Bush claims that is.

“It’s a problem of lack of will, of lack of technology and, particularly, lack of focus,” Senator Schumer of New York, the head of the Senate Democrats’ campaign efforts, said yesterday.

Partisanship has rarely been more in-your-face. Old saws like “politics stops at the water’s edge” have been discarded.

Yet over-politicizing the September 11, 2001, attacks and the war on terror “is a danger both parties face,” a Republican National Committee member from New Hampshire, Tom Rath, said.

Mr. Rath said many people in his largely conservative state accept Bush’s argument that the war in Iraq and the war on terror are linked but do not like to see too much partisanship injected.

The fifth anniversary itself helped “sober people up for a day,” Mr. Rath said. “Despite how either side might want to spin it, the fact is that people remember where they were, what they were doing, how they felt. And I think that’s going to make it harder to use it in a partisan sense for either side.”

What happened to that spirit of bipartisanship?

“What happened to the spirit is life returned to normal in many ways, and people ended up having political disputes,” White House spokesman Tony Snow said. “It’s human nature.”