First and most important, nothing substantive happened last night in terms of changing the dynamic of the GOP race. Rudy Giuliani entered as the front-runner and remains the front-runner, though there remains a clear opening for Fred Thompson.

Of the "Big Three" announced candidates:

Mitt Romney helped himself with a very solid and smooth performance. For Republican voters who do not know much of Romney he made a good first impression, which is always very important. He was clearly in control of his facts and easily passed the test of looking presidential. His smack down of Chris Matthews' Scooter Libby obsession will win points with Republican voters:

I can tell you that I think it was outrageous for the prosecutor, knowing that Scooter Libby was not the source of the leak, to go ahead and begin interviewing him, gathering information, setting up a case against him. I think it was prosecutorial indiscretion.

He also handled the religion questions deftly and had a great line when asked about Roman Catholic bishops refusing communion to pro-choice politicians: "I don't say anything to Roman Catholic bishops. They can do whatever the heck they want."

Rudy Giuliani was calm and confident though the disproportionate amount of time on social issues (abortion, embryonic stem cells, and Terri Schiavo) succeeded in highlighting his distance from many Republican primary voters. While he certainly can improve his delivery and the ease with which he discusses pro-life issues, Giuliani did himself an immense favor by responding honestly on the matter of abortion and not pandering in his answers. More importantly, of all the 10 candidates on stage Giuliani did the best in clearly laying out what the Republicans will press to be the defining issue of the 2008 campaign, which came in a response to the silly question about Bill Clinton being back in the White House:

It would mean that we were back on defense against terrorism, given Senator Clinton's recent positions. And the reality is, in the 1990s, we were on defense in dealing with Islamic fundamentalist terrorism.

When you had this debate last week and all the Democrats were up here, I never remember the words "Islamic fundamentalist terrorism" being spoken by any of them.

From the GOP perspective this is exactly how they want to frame the election in 2008. And he hammered this point home a few minutes later with a question meant to elicit an attack on President Bush:

I think we should remind ourselves, because I remember it every day, that on September 11, 2001, we thought we were going to be attacked many, many times between then and now. We haven't been. I believe we had a president who made the right decision at the right time -- on September 20th, 2001 -- to put us on offense against terrorists. I think history will remember him for that, and I think we as Republicans should remind people of that.

Quite simply, this is the single most important issues for Republican voters and Giuliani drilled it home in a way the others candidates did not. The many pundits who are over-analyzing Giuliani's less than crisp abortion remarks are overestimating the importance of abortion and underestimating the centrality of the war against Islamic fundamentalist terrorism to Republican voters.

John McCain missed a tremendous opportunity. His staunch defense of pushing for victory in Iraq has been slowly getting many conservatives to give the maverick from Arizona another look. As Giuliani's early big lead in the polls has predictably begun to shrink, McCain has been holding steady around 20% in the RCP Average. But while he did not materially stumble last night, he was clearly not at ease; he was overly aggressive; and as the veteran presidential aspirant in the field and the one candidate on stage who has been through this before, he did not display the calmness and confidence that he is capable of. A missed opportunity.

Of the second-tier candidates, no one looked ready to break out as a dark horse capable of running with the Big Three. Duncan Hunter probably won a few converts with a forceful demeanor and a strong national defense message and he stood out among the field with a line that probably won him respect among many Republican voters:

Right now Iran is moving equipment into Iraq that is being used to kill Americans. Iran has crossed the line, and the United States has absolute license at this point to take whatever actions are necessary to stop those deadly instruments from being moved across the line, being used in explosives, roadside bombs, inside Iraq.

Sam Brownback, who is the candidate most identified with pro-life issues, helped Giuliani with this answer:

MR. HARRIS: Could you support a nominee of your party who is not pro-life?

SEN. BROWNBACK: I could because I believe in the Ronald Reagan principle that somebody that's with you 80 percent of the time is not your enemy; that's your friend and that's our ally. And this is a big coalition party, and it's a coalition party that's governed for a number of years in this country. And it governs because it governs with a coalition of economic and social conservatives and people that want to be strong for the United States.

Sounds to me like Senator Brownback is open to a Giuliani/Brownback ticket.

In summary, not much changed last night in California. Romney was the biggest winner of the top-tier candidates simply because he made the most of his opportunity to make a first impression with Republican voters. Giuliani did nothing to jeopardize his status as the front-runner and, notwithstanding all of the focus on abortion, helped himself by drilling home the message of the need to be on the offensive against Islamic terrorism. McCain did not hurt or help himself, which, given his slow drift down in the polls over the last year and his sub-par first quarter fundraising, has to be seen as a disappointment. In the second-tier no one looks capable of becoming a serious threat for the nomination.

The door is still clearly open for Fred Thompson.