COLUMBUS, OHIO: In a marked switch from his previous conciliatory tone, likely GOP presidential nominee Bob Dole Friday called stubborn delegate-poor contender Pat Buchanan "a commentator, not a candidate," and dismissed Buchanan's accusations that Dole has no new ideas. Buchanan Thursday kept speculation alive that he might start a third-party movement if the Republican party takes a "sharp turn to the left." Dole had kinder words for Steve Forbes, whom he said brought a useful message to the campaign in his flat tax proposal. Forbes withdrew from the race after a dismal performance on Super Tuesday, endorsing Dole and offering to help his campaign any way he could. Campaigning Friday in Columbus, Dole highlighted developing Republican unity, and tried to focus his campaign on the upcoming election, challenging President Clinton to produce a balanced budget plan by November.