Newt Gingrich’s surging candidacy seems to have united the conservative establishment — against him.

With Gingrich’s win last week in South Carolina and strong prospects in Florida’s primary, conservative figures and media outlets have been amping up their attacks on a presidential candidate they deem erratic and a potential disaster for the Republican Party.

Gingrich was the subject of twin hits Thursday by National Review, the bible of conservative thought founded by William F. Buckley Jr. The biweekly magazine, which has inveighed against Gingrich for weeks, published a blistering anti­Gingrich statement on its Web site by former senator Bob Dole (Kan.) and a scathing commentary by former Ronald Reagan aide Elliott Abrams.

“If Gingrich is the nominee it will have an adverse impact on Republican candidates running for county, state, and federal offices,” wrote Dole, who supports former Massachusetts governor Mitt Romney. “Hardly anyone who served with Newt in Congress has endorsed him and that fact speaks for itself.” The National Review said the statement came from the Romney campaign.

He added that Gingrich’s nomination “could result in a landslide victory for Obama. . . . Democrats are not running ads against Gingrich, which is further proof they want to derail Governor Romney.”

Abrams wrote that Gingrich, while in Congress in the 1980s, “spewed insulting rhetoric” at Reagan and was unhelpful in the president’s efforts to defeat communism. “Gingrich was voluble and certain in predicting that Reagan’s policies would fail, and in all of this he was dead wrong,” wrote Abrams, who was an assistant secretary of state under Reagan and President George W. Bush’s deputy national security adviser.

The commentary, which was linked to on the widely read Drudge Report, concluded that “Ronald Reagan turned out to be a far better student of history and politics than Gingrich.”

In addition to Dole, Gingrich was rebuked by another Republican he served with in Congress: Tom DeLay (Tex.), who called Gingrich “erratic” and “undisciplined” in an interview Wednesday with a Houston radio station. DeLay was a key figure in one of Gingrich’s signature victories — the Republican Party’s takeover of the House in 1994 — as well as in the 1997 rebellion by House Republicans that forced Gingrich’s resignation as speaker.

Conservative media figures such as George Will, Charles Krauthammer and Ann Coulter have sharply questioned Gingrich’s viability and integrity for weeks. But the criticism seems to be rising.

“His win in South Carolina focused everyone’s mind,” National Review editor Rich Lowry said in an interview Thursday. “If he wins in Florida, he’ll be the front-runner and he’ll have a serious chance to be the nominee. If someone has been on the sidelines about him, they’re running to get on to the field now.”

The National Review devoted a December issue to bashing Gingrich, depicting him as the cartoon character Marvin the Martian on its cover and running essays attacking parts of his record.