With four weeks to go and the entire electorate engaged in this presidential election, what line of attack holds the most promise for John McCain — and for that matter, Barack Obama?  Both campaigns have to find a message that resonates with voters at this moment in order to win their allegiance, especially those in the center who still have not yet decided whom to support.  With the media focused on the global financial crisis, that means the 1992 James Carville equation applies: it’s the economy, stupid.

John McCain has used five basic lines of attack in the last few weeks against Barack Obama:

1. William Ayers and his radical past
2. Fannie Mae collapse and Democratic responsibility
3. Foreign policy
4. Tax-and-spend liberal
5. Chicago politician, not reformer

All of these can help McCain and hurt Obama, and certainly campaigns can carry more than one theme at a time.  However, there is an opportunity cost to pushing less-resonant themes.  It wastes resources that could be used for better messaging, and could backfire by painting a candidate as out of touch with the real concerns of the electorate.

Of these five, then, #2 and #4 look to be the most promising.  Painting Obama as a tax-and-spend liberal is rather easy, and the McCain campaign has done that for months.  Obama promises hundreds of billions in new spending, and since we’re already in deficit spending, Obama has to raise revenues to pay for his new programs.  He can’t tax the rich alone to get that kind of money, and Obama refuses to offer even one program that he’d cut during an economic crisis.

Unfortunately, Republicans use this attack line too often to make it resonate well in this election, true though it may be.  The economic crisis gives McCain a wonderful opportunity to make #2 the main attack theme of the last four weeks.  Americans are angry over the collapse of Fannie Mae and Freddie Mac and the poison they spread throughout the financial sector.  Democrats have begun calling it a failure of “deregulation”, but they spent years protecting Fannie and Freddie from regulators who saw the rot from the inside.  McCain tried pushing legislation to strengthen regulation on the two GSEs.

McCain has to redefine this crisis to the reality of Democratic (and Republican) indifference to the corruption and bad business practices of Fannie and Freddie.  He has to argue that government distortion of lending markets for political gain created the crisis, and that Democratic defense of the GSEs delayed regulatory action until it was too late — and Barack Obama stood on the sidelines and did nothing to stop the collapse.

McCain sponsored legislation; Obama wrote a letter.  McCain took action; Obama did nothing but talk, and far too late.  That has to be the message — and it’s a winner.

Update: Here’s the AOL Hot Seat Poll. They had to condense the question and answers for space, but the post gives the key: