Democratic presidential contenders are campaigning vigorously ahead of voting Tuesday in seven U.S. states that could determine who challenges President Bush in the November election.

The Democratic front-runner, Massachusetts Senator John Kerry, has switched his campaign focus away from his democratic rivals. Instead, he is concentrating on President Bush and what he calls the administration's "reckless" foreign policy.

Opinion polls show Senator Kerry with a commanding lead in most of Tuesday's balloting. One survey by CNN/Los Angeles Times gives the Massachusetts senator a 26-point lead in Missouri, and a seven point lead in Arizona. Missouri has the highest delegate count with 74, while Arizona has 55 delegates; 2,162 delegates from 50 states are needed to win.

The race for second place remains a toss-up between former General Wesley Clark and North Carolina Senator John Edwards.

Former front runner and ex-Vermont Governor Howard Dean has seen his campaign falter in recent weeks. He criticized Senator Kerry on Saturday, calling him a special interest clone. He also said the senator is not capable of beating President Bush in the upcoming election.

The three other Democratic candidates are Senator Joseph Lieberman of Connecticut, civil rights activist Al Sharpton, and Ohio Congressman Dennis Kucinich.

The seven Democratic primary elections and caucuses to be held Tuesday in Missouri, Arizona, South Carolina, New Mexico, Oklahoma, Delaware and North Dakota will send 269 delegates to the Democratic National Convention later this year.