Barack Obama overtook Hillary Clinton in the race for the Democratic nomination in the latest primaries in Maryland, Virginia and Washington DC.
On the Republican side John McCain confirmed his dominant front-runner status.
The videos below show the candidates' own reactions to the results - and other highlights of their campaigns so far.
After losing the Wisconsin primary, Hillary Clinton has urged Americans to consider the impact of their votes on the future of the country.
The former first lady has criticised Barack Obama's leadership credentials.
Barack Obama has won the Wisconsin Primary over Hillary Clinton.
Mr Obama has assured voters he is ready to be president and bring fresh ideas to the White House despite his relatively short political career.
Republican candidate John McCain has assured voters that he is able to meet the challenges facing the future president.
Mr McCain was buoyed by confidence after winning the Wisconsin vote, making him the Republican party nominee.
The former governor of Arkansas has been under pressure to stand aside for the sake of Republican unity, but has said he has no intention of pulling out.
Speaking after his earlier victories in Kansas and Louisiana, Mike Huckabee said "I am not in the race to be a fly in the ointment".