As Congress mulls a sweeping $700 billion bailout of soured U.S. mortgage investments, the presidential contenders continued to offer their views on the handling of the Wall Street crisis in campaign appearances and newly launched ads.

Speaking Monday morning on NBC’s “Today” show, Republican presidential nominee Sen. John McCain said, “We are in the most serious crisis since World War II.” McCain also said that despite a growing national debt, he would not raise taxes if he were elected.

Speaking to voters in Scranton, Pa., McCain called for greater supervision over the proposed bailout plan and expressed concern over the singular power the treasury secretary will have to allocate billions in taxpayer dollars.

“Never before in the history of our nation has so much power and money been concentrated in the hands of one person. This arrangement makes me deeply uncomfortable,” McCain told an Irish-American group in the battleground state. “We will not solve a problem caused by poor oversight with a plan that has no oversight.”

McCain told a Baltimore crowd over the weekend that he would provide “comprehensive reform to the broken institutions” of Wall Street and said he would help “keep people in their homes and safeguard the life savings of all Americans.”

McCain also took a swipe at his rival, Democratic presidential nominee Sen. Barack Obama, saying that Obama had “declined to put forth a plan of his own. At a time of crisis, when leadership is needed, Sen. Obama has not provided it. We saw the same lack of leadership on Iraq.”

For his part, Obama called the proposed $700 billion bailout “staggering” on Saturday. The Illinois senator said that the final measure should include protection for U.S. taxpayers, a commitment to new regulatory reforms for Wall Street and have broad bipartisan support.

During a visit to Charlotte, N.C., Obama told supporters that the current financial crisis can be linked back to GOP economic policies.

Obama told the crowd, “We’re now seeing the disastrous consequences of this philosophy all around us … And yet Senator McCain, who candidly admitted not long ago that he doesn’t know as much about economics as he should, wants to keep going down the same, disastrous path.”

In what his campaign billed as a major economic speech in Green Bay, Wis., Monday Obama called for major reforms to make government more transparent and for curbs on the influence of lobbyists.

“We are facing a financial crisis as profound as any we have faced since the Great Depression,” he said. “As a result, your jobs, your savings and your economic security are now at risk. This week, we must work quickly, in a bipartisan fashion, to resolve the crisis and avert an even broader economic catastrophe.”

In the speech, Obama accused Republicans of fostering an “era of greed and irresponsibility on Wall Street and in Washington.”

Both candidates released new television ads Monday. Obama’s claims that McCain’s proposal to deregulate health care could prove disastrous, having an impact similar to those now reverberating through Wall Street.

McCain’s ad hits back, claiming that Obama is a product of “Chicago’s corrupt political machine” and criticizing his economic advisers.