The conservative tide ebbs, the progressive tide flows

American politics reached a pivot point this week. A new story line will now define how voters and the media see what's going on.

Since election day in 2010, the prevailing narrative has been about a resurgent conservatism, a president on the defensive, big government under attack, the deficit as the dominant issue, andthe Tea Party as the political system's prime mover.

The backdrop for this saga has been an ailing economy. The troubled economy, alas, is still with us. But everything else is in flux.

Consider the week's three jolts to the system:

First, the decision of New Jersey Gov. Chris Christie to forgo the Republican presidential contest almost certainly settles the party's field. This means that the next several months will be all about Mitt Romney and what it is he actually believes.

Romney wants to keep running against President Obama and a bad economy. His opponents -- especially Texas Gov. Rick Perry, still his leading rival despite numerous missteps -- want the contest to be about ideology and Romney's shortage of discernible philosophical commitments.

The more the race highlights ideology, the more uncomfortable things will get for Romney.

"Does he not believe in rebuilding America's roads and bridges?" Obama asked. "Does he not believe in tax breaks for small businesses or efforts to help our veterans?"

Americans are clearly fed up with "Washington" and "politics." Obama's move shows how determined he is to remind the country that he doesn't run the government all by himself and that Republicans in Congress are now incumbents and not just the opposition.

He will cast himself as the guy with ideas and Republicans as cranky reactionaries who will keep anything good from happening.

Finally, the anti-Wall Street demonstrators have created a new pole in politics. Americans have always been wary of concentrated power.

The Tea Party had great success in focusing anxieties on what it argues is an excessively powerful federal government.

Note that both Obama's initiative and the revolt against Wall Street mark a shift on the progressive side from defense to offense.

Over the last several weeks, talk about the deficit and spending has receded, replaced by a new dialogue on job creation, fairer taxes and the abuses by financiers that got the country into economic difficulty in the first place.

And the Tea Party has come under heightened scrutiny, thanks to members of Republican crowds who booed a gay soldier and cheered at the mention of both executions and the prospect that an uninsured citizen might be left to die for failing to buy health coverage.

Romney knows that he needs to appease the Republican right while escaping its embrace. He recognizes that by directing his fire toward Obama and the dismal economy, he can simultaneously unite the GOP and appeal to swing voters.

He wants to give Republican primary voters just enough conservative ideology to win just enough of their votes to capture the nomination.

This makes him safe as an alternative to Obama. But many conservative voters also suspect Romney doesn't believe all that he's saying.

This pushes them toward other candidates. Perry and the other candidates have an interest in aiming straight at this tension in the Romney strategy. Democrats hope they do just that.

In the meantime, Republicans in Congress find themselves defending a series of unpopular positions. Voters don't like tax increases in general, but they do think the wealthy should bear a bigger share of the tax burden.

Regulation may be an easy target, but Americans are in no mood to let Wall Street off the regulatory hook. And government may be scorned in the abstract, but the specifics of what Obama wants government to do through his jobs bill have wide appeal.