WASHINGTON — The Super Tuesday primaries were a test of strength that demonstrated weaknesses in both parties and pointed to problems each could confront in the fall.

With Mitt Romney’s decision to leave the race on Thursday, John McCain’s nomination is a near certainty. But he leads a party torn by ideology and has survived only because his conservative opponents have fractured their movement.

Hillary Clinton and Barack Obama fought to a near draw in a series of Democratic primaries that revealed a sharp gender gap, a generation gap at least as deep as the age divide that was so widely advertised in the 1960s, and differences across lines of ethnicity, race and class.

Clinton could count herself lucky in surviving a national wave toward Obama that began building after the bitter South Carolina primary.

Important states that her campaign feared might stray — New Jersey, California and Massachusetts — stuck with her. She won them with strong support among women, whom she always saw as her ballast in stormy moments.

As they did in New Hampshire, women allowed Clinton to fight another day.

But a Clinton campaign that once hoped it could use Tuesday’s contests to dispatch a young challenger with just over three years of Washington experience found itself facing a well-organized opponent capable of winning 13 (and possibly 14) states as diverse as Idaho and Georgia, Alaska and Missouri. In the short run, the political map favors Obama, who has steadily gained ground as he has become better known.

Yet whatever divisions the Democrats face, it is the Republicans who have confronted an ideological civil war in which popular talk show hosts — in vain as it turns out — served as field generals determined to beat back McCain’s advancing army of Republican dissidents.

Despite his impressive victories, McCain continued to fare poorly on Tuesday among the conservatives who have defined the Republican Party since the rise of Ronald Reagan.

McCain came to dominate the Republican contest because moderates and liberals, opponents of President Bush and critics of the Iraq War, continued to rally to him despite his actual stands on the very issues that arouse their ire. And he prevailed because Mike Huckabee and Mitt Romney continued to divide the right.

Huckabee became the champion of the Old South, winning in Arkansas, Tennessee, Georgia and Alabama, and he nearly defeated McCain in Missouri and Oklahoma. Romney won a swath of states in the Midwest and mountain West.

McCain, in other words, lost the core Republican states and instead piled up delegates in New York, New Jersey, Connecticut, Illinois and California. All are traditionally Democratic states unlikely to vote for him in November. Rudy Giuliani’s strategy, which was premised on his strength in such places, actually worked — but it worked for John McCain.

Huckabee’s showing doomed Romney’s chances of uniting conservatives behind his candidacy. This may only aggravate the frustration of McCain’s critics on the right, who looked on powerlessly as a starched investment banker and a good-natured preacher split asunder their party’s natural majority.

Clinton and Obama face different challenges. Democrats have declared in poll after poll that they like both of them, but the two have reached parity in part because of difficulties each has with important constituencies.

Obama is the overwhelming favorite of voters under 30, and he has inspired a disciplined army of youthful organizers who helped him win decisive victories in caucuses in Colorado, Kansas, Idaho, Minnesota, North Dakota and Alaska. If Clinton is the nominee, how many of these young voters will walk away from a process that thwarted their hopes?

Sisterhood has certainly been powerful for Clinton. But does her weakness among male Democrats — she lost men by 20 points in Delaware, 21 points in Connecticut and 39 points in Georgia — portend problems in a general election?

For his part, Obama has consistently lost badly among voters over 65 who are white or Latino. Outside his home state of Illinois, he has yet to make serious inroads among white working-class voters who were central to Clinton’s victories in states such as Massachusetts and New Jersey. Obama will need a larger share of these voters in the coming Ohio showdown in March and, possibly, in Pennsylvania in April. And he would need them in November.

But the larger challenge is to a Republican Party that faces, simultaneously, an insurrection and a lack of enthusiasm in the ranks.

Super Tuesday anointed McCain as the favorite for nomination. It did not make him the favorite of his party’s most important wing. Now, McCain must appease his conservative critics while not squandering his appeal to middle-of-the-road voters whose sympathy made him his party’s most electable candidate.

E.J. Dionne’s e-mail address is postchat(at)aol.com.

© 2008, Washington Post Writers Group

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