Opinion polls give Democratic candidate lead in traditionally Republican states.
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McCain has been facing sliding numbers in the polls.
A Quinnipiac University/Wall Street Journal/Washingtonpost.com poll on Tuesday – a day before the final televised presidential debate between the rivals – gave Obama, the Democratic presidential nominee, sizable leads in four battleground states.
With three weeks to go until the November 4 election, the two will face each other in their third debate on Wednesday in Hempstead, New York.
The recent poll shift in favour of Obama has been partly attributed to McCain’s perceived weakness on economic issues and his campaign is seeking to reassure voters of his ability to lead the country out of financial turmoil.
“As president, I will also act to protect investors, especially those relying on their investments for retirement,” he told supporters at the rally.
Many older Americans have seen their retirement accounts devastated in recent weeks due to the global stock market crash.
McCain proposed reducing a maximum tax rate for senior citizens on money they withdraw from retirement plans to 10 per cent in 2009 and 2010.
He also reiterated his support for using money under the recently approved $700bn Wall Street bailout package to help homeowners facing foreclosure – a move Obama has condemned as “risky”.
Al Jazeera’s Sebastian Walker, reporting from Pennsylvania, said McCain’s campaign was billing Tuesday’s speech as part of his “comeback strategy”.
“Although some of his staff are concerned they also say McCain is a fighter,” Walker said. “But time is running out and he’s got a lot of work to do.”
Obama unveiled his economic proposals, touted as a “rescue plan for the middle class”, a day earlier in Toledo, Ohio.
The Democrat’s proposed steps would cost $60bn over two years and would include temporary tax credits to help create new jobs, penalty-free withdrawals from retirement accounts, a short-term stay on banks foreclosing on homeowners trying to pay off mortgages and greater lending to states and municipalities.