The man screaming is Rick Santorum, one man Democrats would love to destroy more than any other in next month’s midterm elections. Mr Santorum, the third-ranking Republican in the Senate, has become one of the most polarising polticians in the country thanks to his abrasive social conservatism. And he is clearly not going down without a fight.

Mr Santorum is the most senior Republican incumbent being targeted by Senate Democrats this year and has been trailing his challenger, Bob Casey Junior, the son of a beloved former governor, for months. Nearly everyone agrees this is because the people of Pennsylvania just don’t like Mr Santorum any more.

But there are greater forces working against him other than his 43 per cent unfavourability rating. Republican analysts believe that Mr Santorum’s problems are rooted in the return of white, blue-collar voters to the Democrat fold, a generation after Ronald Reagan wooed them to the Republican cause.

The “Reagan Democrats” have been a cornerstone of Republican electoral success for the past 20 years, especially in the Midwest, still the battleground for presidential contests. By the early 1980s, these traditional Democrat voters — both rural and urban lower middle-class — no longer saw Democrats as their champions. Socially conservative, they were attracted by Mr Reagan’s simple message of moral values, fiscal responsibility and national security. Millions fled to the Republicans and stayed.

Mr Santorum has won in Pennsylvania — he was re-elected to a second six-year term in 2000, in part because his conservatism appealed to blue-collar Democrats. In recent years they have been motivated to vote on cultural issues more than economic ones.

Frank Luntz, a Republican pollster and one of the strategists behind the party’s 1994 takeover of Congress, told The Times: “The Santorum race shows that Reagan Democrats are returning to their roots. Economic issues among blue-collar social conservatives are now subsuming concerns about social issues.

“The Republican party has failed them. It didn’t cut spending. It wasn’t honest. It hasn’t controlled immigration. On issue after issue it didn’t do what these voters expected.” Mr Luntz says that this political remigration of Reagan Democrats — which if realised next month would represent a profound change of the American political landscape — is occurring across the Midwest, where the economy is arguably an even greater issue than Iraq.

Hundreds of factories and car plants have closed, in states such as Michigan, Pennsylvania, Iowa and Wisconsin. Since Mr Santorum first arrived in the Senate at the age of 36, a young Turk riding the conservative wave that swept congressional Democrats from power 12 years ago, he has been an odd fit for the traditionally moderate political terrain of Pennsylvania. Before him, the state had not elected a conservative senator since 1952.

He has voted with Mr Bush 98 per cent of the time, in a state where the President has become very unpopular.

Combined with the tectonic voting shift identified by Mr Luntz, it is little surprise that Mr Santorum has trailed his opponent by 10 points for months.

Mr Casey, an anti-abortion social conservative and trade union economic liberal, is an easy man for a Reagan Democrat to support. Bill Zerbe, 72, a retired salesman, grew up in a conservative Democratic home in south-east Pennsylvania. After voting Democrat, he switched to Ronald Reagan and the Republicans in 1984. “I’m voting Democrat again now,” he said. “I’m disappointed in the Republicans. They’re dishonest. They talk about morals and principles, but do otherwise. Any Democrat gets my vote now.”

BORN IN THE USA: THE HARD-HAT CLASS THAT IS COMING HOME

Times Recommends

• Appalachian voters lean towards Obama
• Iraq: Battle for business begins
• 50 dead in seven days in Mexico's drugs war