"At the same time that we're having a challenging environment, they're having a more challenging environment," he said.
In a speech to the governors, Mehlman also accused Democrats of sending mixed messages on Iraq by attacking President Bush when they seemed to be "in fundamental agreement" with his war policy.
"Are the Democrat attacks designed to help us win the war on terror, or are they designed to help them win the next election?" he asked.
Among those he singled out was House Minority Leader Nancy Pelosi. He criticized her endorsement Wednesday of a plan to withdraw U.S. troops from Iraq within six months, saying the plan would result in U.S. defeat.
Pelosi spokesman Brendan Daly called Mehlman's remarks "the typical Republican line."
"Democrats recognize we need an exit strategy," he said. "We need a clear plan for victory, and we don't have that."
Gov. Arnold Schwarzenegger, who has declined to appear with Bush during the president's last two visits to California, did not appear in public with his fellow Republican governors. Instead, he planned to speak to them privately Thursday at a reception.
Schwarzenegger, who named a Democrat on Wednesday as his new chief of staff, has tried to distance himself from Bush as he prepares to seek reelection next year in a state that has largely shunned the GOP.
But other governors seeking reelection in 2006, including Pawlenty and Linda Lingle of Hawaii, said they would be glad to campaign with Bush.
"It would be disingenuous for Republicans to try to run away from the Republican president," Pawlenty said. "People can see through that."
