So much for the embrace by Barack Obama. This week, John McCain will take the floor and let 'er rip on Obama's stimulus bill. And Mac isn't in the mood for reconciliation. Avlon is the author of Wingnuts: How the Lunatic Fringe Is Hijacking America.

This week, John McCain will take to the floor of the Senate and try to reclaim his role as the leader of the center by pressing for changes to the pork-filled, party-line House stimulus bill—challenging the President to follow through on his bipartisan rhetoric.

"He takes President Obama at his word—that he is open to efforts to make this a better bill," says former McCain campaign manager and confidant Rick Davis.

Despite President Obama's personal outreach to McCain, including an unprecedented Inauguration Eve honorary dinner, there is every indication that the Arizona senator is not in a “go-along, get-along” mood (especially after the Cardinals lost the Super Bowl.) As McCain himself said Friday, "This bill was written by Democrats and without real or any impactful Republican input. It's not the right way to start."

McCain is the de-facto leader of the opposition—a giant in a party of pygmies.

McCain's continued high profile is unusual for former presidential nominees. Senators McGovern and Kerry quietly settled into senior statesman roles. But McCain is the de-facto leader of the opposition—a giant in a party of pygmies, nationally known and still widely respected, despite damage to his brand by association with Sarah Palin and Rove-trained operatives' play-to-the-base politics. The 72-year-old warrior is already planning a 2010 Senate reelection campaign. He is not going to go quietly into that good night; he wants to stay and fight.

And this is a good fight for McCain. Even among Rush Limbaugh-style conservatives, who always saw him as ideologically suspect, McCain has earned high marks as a fiscal conservative crusader against wasteful spending. The growing consensus criticism of the House bill plays right to his strengths. As newly-elected RNC chair Michael Steele said on Fox News Sunday, "It's not a stimulus bill, it's a spending bill—let's call it what it is."

Expect McCain to lead the charge on cutting the bill's Christmas tree appropriations from $150 million for the Smithsonian to $400 million for STD prevention to $6 billion for broadband Internet access. The larger argument will be that while these and other appropriations might be worthwhile on their own, they have little to do with actual job-creation – while less than 5% (or $40 billion) is devoted to infrastructure spending on items like roads and bridges.

The Obama administration thought it would attract GOP support with one-third of the bill dedicated to the Republican Turkish delight of tax cuts, but McCain and others are saying that the proposed tax cuts are insufficient and of the wrong variety—pushing for payroll tax cuts instead of rebates, cuts in the corporate tax rate, and commitments to no new taxes.

McCain is also showing signs of a broader fiscal agenda, beyond the stimulus package. He's been calling for a return to fiscal responsibility—a firm commitment to the deficit hawk principles of Gramm-Rudman after several quarters of GDP growth is achieved. That may be a long way off, but as an advocate of generational responsibility, it's good to see someone in Washington looking to impose balanced budgets again.

That's not all. Expect McCain to refocus on foreclosures and the ongoing mortgage crisis as well, possibly reviving a late-inning campaign proposal for the government to buy up loans from underwater homeowners and renegotiate more affordable terms. The $300 billion plan—borrowed from Hillary Clinton's primary campaign—failed to ignite bipartisan support and came under particular fire from conservatives, but since the fall the foreclosure problem has only grown, with no end in sight.

Democrats don't need Republican support to pass the bill in the Senate, but they want it. They actually lost ground with the House bill's approach, losing the support of 11 Blue Dog Democrats without gaining a single Republican vote. The TARP bailout backlash is working against them, with public cynicism over its largess and lack of evident impact adding to the call for oversight, accountability, and restraint.

Already centrist Senate Democrats are in need of convincing, with Nebraska's Ben Nelson telling MSNBC on Friday, "There's no question that there's a lot of spending in the bill, but what we really need to do is focus on what it does for jobs." Earlier in the day, Nelson hosted a meeting of Republicans Susan Collins and Bob Corker, along with fellow Democrats Mark Warner and Claire McCaskill. These are not Obama-obstructionists, but they could provide streamlined counter-proposals to the liberal-spending excesses of the House bill. None of their votes can be considered a sure thing.

In the past, McCain would have been chairing such a centrist revolt against the party whips, and he might join them still in an update to 2005's Gang of 14. But McCain now has the added weight of a party mantle around his neck. With less to lose and nothing to prove, the maverick is not in a conciliatory mood—he'd rather speak his mind and make a stand. If the center forms around him in the Senate, so much the better, but he does not want to be used by the administration that defeated him as cover for plans he opposes in principle. The fact that fiscal crisis may force his hand makes the gambler grumpy. He had warned against this, after all.

One year ago, McCain was on the verge of winning a nomination that had been denied to him by a lesser man with a low-road campaign eight years before. His centrist rhetoric and record had been ahead of their time. But now economic storm clouds were gathering, with Republicans' credibility in tatters. The old veteran could see what was coming—he only underestimated the scale: "You're going to hear from the Democrats, let's pump $70 billion, let's pump $80 billion, let's do this, let's do that. My friends, remember who's going to pay that. It doesn't come off a printing press, okay? It comes out of your pockets."

John P. Avlon is the author of Independent Nation: How Centrists Can Change American Politics. Avlon also served as director of speechwriting and deputy director of policy for Rudolph Giuliani's presidential campaign, and previously served as chief speechwriter and deputy communications director for Mayor Rudolph Giuliani.