Sen. John McCain, acknowledges the cheers of supporters during the last night of the Republican National Convention in St. Paul, Minnesota, 04 Sep 2008

U.S. Senator John McCain is making his first campaign appearances as the official Republican presidential nominee Friday, with stops in Wisconsin, Michigan and Colorado.

At a rally in the upper midwest city of Cedarburg, Wisconsin, McCain promised to tackle corruption and special interests in the nation's capital.

McCain formally accepted the nomination Thursday on the final day of the party's national convention in St. Paul, Minnesota. 

In his acceptance speech, the veteran Arizona lawmaker embraced his image as a "maverick" who works across party lines.  He promised that he and his vice presidential nominee Governor Sarah Palin of Alaska will reform Washington.

He said his own party lost the trust of the American people when some Republicans gave into the temptations of corruption.

But McCain said he has big differences with his Democratic opponent, Barack Obama.  He criticized the Illinois senator on a number of issues, including the economy, education and energy.

In a statement Friday, Democratic vice presidential nominee, Senator Joe Biden, challenged McCain's record of bipartisanship, noting he voted with President George Bush 90 percent of the time.

Democratic presidential candidate, Sen. Barack Obama greets supporters in Buchanan Park in Lancaster, Pennsylvania, 04 Sep 2008

A statement issued earlier by the Obama campaign said McCain ignored the fact that the Arizona senator was part of the "do-nothing" crowd in Washington for nearly 30 years. 

New York Senator Hillary Clinton, Obama's rival for the Democratic nomination, also issued a statement Thursday dismissing the Republican convention.  She said McCain and Palin offered no new solutions to fix the economy, provide affordable health care and guarantee equal pay for female workers.

During a campaign stop in Pennsylvania Friday, Obama criticized McCain's energy record, saying that during his 26 years as a lawmaker he has been against developing alternative fuels.

Some information for this report was provided by AP and Reuters.