McCain’s big lead in this new national poll matches a wave of increasing support seen in state polls, which, coupled with the GOP’s winner-take-all rules, gives him the opportunity to effectively wrap up the nomination with a strong showing Tuesday.

The Democratic contest is likely to keep going.

Democratic delegates are doled out based on complex formulas, with candidates picking up backers based on their performance within states and within congressional districts. The new poll underscores how competitive the race continues to be.

While Clinton has the edge on the issues voters say are most important to them, and enjoys a wide lead on the question of who is a stronger leader, Obama now holds a seven-percentage-point advantage as the candidate who would do the most to bring needed change to Washington.

And Clinton’s once-sizable lead as the Democrat with the best shot at winning the White House has shrunk significantly; in the new poll, 47 per cent said she is the most electable, while 42 per cent said Obama has the better chance. In hypothetical general-election matchups, both Democrats run neck-and-neck with McCain, and both lead Romney by double digits.

McCain outperforms Romney in the general-election tests because he picks up significantly more support among independents and political moderates. These groups have been crucial to the senator in early-state caucuses and primaries, and his biggest gains in this poll came among them.

McCain has taken control of the GOP race by picking up mainline Republican supporters as well. Nearly half of self-identified Republicans now support him, up nearly fourfold from December. He appears to have benefited from the decisions by former New York Mayor Rudy Giuliani and former Sen. Fred Thompson of Tennessee to quit the race. Both Giuliani, who has endorsed McCain, and Thompson appealed to many of the voters McCain now counts in his camp.

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