WASHINGTON  The Democrats like to say that electing Senator John McCain would usher in the third term of George W. Bush, and they do not mean it as a compliment. The Republicans counter that calling the senator “McBush” is political spin and that Mr. McCain is his own man.

A look at Mr. McCain’s 25-year record in the House and Senate, his 2008 campaign positions and his major speeches over the last three months indicates that on big-ticket issues  the economy, support for continuing the Iraq war, health care  his stances are indeed similar to Mr. Bush’s brand of conservatism. Mr. McCain’s positions are nearly identical to the president’s on abortion and the types of judges he says he would appoint to the courts.

On the environment, American diplomacy and nuclear proliferation, Mr. McCain has strikingly different views from Mr. Bush, and while he shares the president’s goals in Iraq, he was at times an outspoken critic of the way the war was managed.

The disparities between the two are murkier on other issues. On immigration, Mr. McCain started out with Mr. Bush  at odds with the Republican mainstream  by favoring a path to citizenship for millions of illegal immigrants, then backed off and emphasized the border-security-first approach favored by a majority of his party.