Up to 50,000 protesters are expected at the inauguration of George W Bush.
It is likely to be the biggest demonstration against a new president since Richard Nixon was re-elected.
The protesters are demanding that Mr Bush recognises he was elected with a minority of the national vote.
More than a dozen protest groups claim Bush is anti-women, anti-public education, anti-minority, anti-environment, anti-gay and anti-health care.
They also claim he is pro-prison, pro-execution and pro-corporate interests.
One protest group, International Action Centre, has filed lawsuits against the police, claiming plans for check points to screen people approaching the parade route are unconstitutional.
Bush supporters' website LoudCitizen, which is organising a National Patriot's March to celebrate what they see as a constitutional victory, claims that "anti-Everything" organisations are wrong to portray Bush's victory as illegitimate.
The police are promising the tightest security ever for the demonstrations with 5,200 officers present.