The president's news conference today may have marked a turning point in his young presidency.

A White House Press Corps that had been ridiculed for its allegedly fawning coverage was asking tough questions. And a president noted for his easy self-assurance was defensive and even testy at times. He insisted there was nothing new in his tough, and unmistakably new, language on Iran. He never did answer the question of whether the invitation still stands to Iranian diplomats to come to U.S. embassies around the world to celebrate the 4th of July.

These are critical and difficult days for Mr. Obama. His job approval ratings, while still high, have fallen. His support among independents, the crucial swing vote in American politics, has dropped from 60 percent in April to 45 percent now.

His health care proposals are in some trouble on Capitol Hill, amid growing public alarm about the staggering amount of deficit spending they will require. The proximate cause of that worry, of course, is the $787 billion spending spree he let Congress embark on in the name of economic stimulus last winter.

The unemployment rate that spending was supposed to hold below eight percent has raced past nine percent and is still rising.

In the beginning, it seems, charm and style count, but in the end it's the results that count most.

Brit Hume is the senior political analyst for FOX News Channel.