With the latest wins on Saturday, Kerry has won 14 of the 16 Democratic contests so far and has emerged as the clear favourite to challenge US President George Bush in November's presidential vote.
"With George Bush's bad record- with his lack of vision- he has no choice but to resort to attack politics. Maybe we can't blame him, but come November, we can replace him," a confident Kerry said in remarks prepared for a party dinner in Milwaukee.
With 100% of precincts reporting, Kerry had 62.9% of the ballots cast in Nevada. Rivals Howard Dead trailed with 16.8% and John Edwards with 10.4%.
Kerry's win in Washington DC was equally emphatic. With 100% of precincts reporting, Kerry bagged 47%. Civil rights activist Al Sharpton came next with 20%. Dean was placed third with 17% followed by Edwards at 10%.
Kerry, the only candidate to campaign in Nevada, began the day on Saturday telling supporters at a caucus site at a Las Vegas high school he was "astounded and grateful" for their support.
The front-runner has largely ignored his rivals on the campaign trail to keep the focus of his criticism on Bush.
In Milwaukee, he hammered Bush for sending supporters a link to an internet video earlier this week that attacked what it said were Kerry's ties to special interests.
"Instead of attacking America's problems, George Bush has decided to play attack politics," Kerry said.