The nation’s deepening economic problems, having taken their toll on McCain’s candidacy, have recently led to his campaign increasingly focusing questions about Obama’s character and background. With a little more than a fortnight to the presidential election, McCain campaign has resorted to automated phone calls that link Barack Obama to the 1960s radical, William Ayers.

The most recent development has McCain’s campaign and the Republican National Committee sending at least four different recorded telephone messages to voters in about a dozen battleground states, including Maine and New Hampshire.

The call goes thus: “You need to know that Barack Obama has worked closely with domestic terrorist Bill Ayers, whose organization bombed the US Capitol, the Pentagon, a judge’s home, and killed Americans.”

This move has irked the Senators in opposing political parties, who have asked McCain to stop such ‘robo calls.’ Individual appeals towards this end have come from Senate Majority Leader Harry Reid - a Nevada Democrat, Sen. Norm Coleman - a Minnesota Republican, and Sen. Susan Collins - a Maine Republican.

At a news conference in Las Vegas, Reid told reporters that he is surprised at the “scummy” tactics employed by McCain’s presidential campaign and “can’t believe John McCain knows what’s going on.”

Collins spokesman, Kevin Kelley, said: “These kind of tactics have no place in Maine politics. Sen. Collins urges the McCain campaign to stop these calls immediately.”

However, the McCain campaign combated the disapproval of its latest move, saying that the calls are warranted because Obama’s association with Ayers - the two met many years after Ayers’ anti-Vietnam War activities had ended - raises questions about the Democrat’s judgment and record.

McCain spokesman, Rick Gorka, said: “This is an association that is highly questionable and not out of bounds.”

The spokesman for Obama campaign, Tommy Vietor, expressed his reaction saying: “Senator McCain calls Ayers an old, washed-up terrorist. If that’s the case, why is he spending all this money on these nasty, dirty, robocalls?”