I had thought out in advance a week ago or more what John McCain needed to do tonight. But for better or for worse (in a macro sense, for McCain, probably worse) the financial crisis and McCain’s decision to double down on getting a deal done in DC, followed by his unsuccessful game of chicken aimed at getting Obama to postpone the debate, has totally scrambled the situation and thrown everything into chaos. These kinds of structured Q&A debates aren’t really either candidate’s strong suit – Obama’s better at staged speeches, McCain at wide-open forums – but in McCain’s case, the advantage he has is that this is head to head, so he can have some effect on his opponent’s performance.

Since he’s had a bad two weeks in the polls, he has a greater need to move the needle than Obama does; the stakes are high. Beyond the general need to avoid major gaffes and serious no-nos (for McCain, having a ‘senior moment’ or doing something people see as racially insensitive, for Obama, hitting McCain for his war-related disabilities again or otherwise giving McCain a good reason to play the war hero card), here is what McCain needs to do.

(1) McCain needs to sell what he has been doing this week.

Foreign policy debate or no, the elephant in the room is the credit crisis, the negotiations in Washington, and McCain’s brief suspension of his campaign. He needs to address, not necessarily at length but squarely, that he’s been hard at work in DC and that a bipartisan deal will get done and will justify his decisions. (Implicitly it reminds people that McCain’s been too busy to prepare for this debate, he’s going in cold because he knows his stuff). If no deal gets done, this race is over, and McCain and everyone else know it.

Relatedly, McCain needs to be on the offensive in getting economic issues, including energy security and free trade, into this debate. One of the risks he’s faced all campaign is that he’d be seen as a foreign policy guy with no real interest in domestic bread-and-butter issues; with those issues dominating the week’s news, he needs to communicate that they are very much on his mind.

(2) McCain needs to punch Obama in the face.

Rhetorically, of course. Given the seriousness of this week’s events it may be a bit riskier to do it tonight, but he needs to start and to do it in each of the debates. From McCain’s perspective, you usually worry about coming off as mean, but people generally don’t think John McCain is a nice man; they like and/or respect him because he’s a scrapper who is willing to throw a punch and gets up off the mat when you hit him. And especially in the national security area, one of the largest concerns about Obama is his toughness; McCain wants the viewer at home wondering how Obama will stand toe to toe with Ahmadenijad or Putin.

Going after Obama very directly is good as well for the body language; Obama tends to stare at his shoes and look sheepish when he’s criticized, and he’s extremely thin-skinned and reacts badly to being directly criticized or called out on untruths. For example, Obama will claim that Bush and Maliki are following his plan for withdrawals from Iraq by mid-2010; McCain needs to hammer home that Obama’s plan in fact called for complete withdrawal by March 2008.

(3) McCain needs to keep Obama off balance.

This much, he’s already done; Obama has had his schedule and focus seriously disrupted this week. McCain thrives on chaos and crisis; Obama does not. McCain needs to keep rattling Obama, keep him out of his comfort zone of gauzy generalities, and force him to answer questions he hasn’t thought through.

(4) McCain needs to raise doubts about Obama’s staying power in Afghanistan.

The Democrats for some time now have followed a strategy of balancing dovish policies on wherever the U.S. is engaged in a hot or cold war with tough talk about other enemies we aren’t confronting at the moment – hence, Democrats talked tough on Iraq in 1998 but not in 2002, or on Iran in 2004, but less so in later years as an actual confrontation became a possibility. But Obama’s extended the tough talk to Afghanistan, where we are actually at war.

But once withdrawals from Iraq accelerate and Bush is gone, the anti-war movement’s focus will inevitably shift to Afghanistan. If the fight there gets tougher, will Obama have the guts to take the position McCain did with Iraq in 2007-08 and double down for victory, or will he do what Obama did in that period? McCain has to draw that connection to show how Obama’s faux-hawkishness will melt under pressure.

(5) McCain needs to start identifying Obama as an arch-liberal.

This is more an issue for the domestic policy debates but it needs to start tonight. At the end of the day, America is a slightly center-right country. McCain is a center-right candidate, the candidate for people who are a step to the left of George W. Bush; Obama is a far-left candidate, the candidate for people who are a step to the left of Hillary Clinton. Yet much of Obama’s appeal is the fiction he started building in 2004 that he was some sort of centrist unity candidate. McCain has to shatter the remains of that illusion.

The face to face debates are the best time to drive that point home, both explicitly and through the issues. He can, for example, remind people that this time last year, Obama was promising liberal groups he would “slow our development of future combat systems.” In 2004, simply by repeatedly calling John Kerry a liberal in the second debate, President Bush drove up by 6 points in one night the number of people who identified Kerry as a liberal.

Also, one bit of advice for Obama:

Obama needs to ignore Palin

Obama has a lot of trouble letting things go, and has shown a particular problem handling the prominence of McCain’s running mate, which leads to lowering Obama’s stature by reminding people that McCain’s far more experienced and prepared than the two of them put together. Obama should deal solely with McCain.