Jim Rutenberg
and Jeff Zeleny

TROY, MICH.: Whether Mitt Romney wins or loses the Michigan and Arizona primaries Tuesday, his advisers are warning donors and other supporters to prepare for a longer, more bruising and more expensive fight for the Republican presidential nomination, which may not be settled until at least May.

That campaign trail reality is prompting a new round of intensified fundraising by his financial team, which had hoped by this point to be collecting money for a general election match with President Barack Obama. The campaign is increasingly trying to quell anxiety among Republican leaders, while focusing on the mechanics of accumulating delegates needed to secure the nomination.

Romney’s aides said they were confident that their sustained attacks portraying Rick Santorum as a Washington insider, and Santorum’s shaky debate performance in Arizona on Wednesday, had blunted their rival’s recent surge in Michigan.

But Romney is by no means in the clear, they said, as he fights to avert a loss in the state where he was born and reared — and where he was expected to handily win less than three weeks ago, before Santorum scored surprise triumphs in Colorado, Minnesota and Missouri.

On Saturday, both candidates made appeals to conservatives at a gathering of the group Americans for Prosperity. Santorum, who was received with booming applause, lit into Romney, calling him a politically pliable elitist whose Massachusetts health-care plan and selective support for bailouts — for Wall Street’s, against the auto industry’s — disqualified him to be the party’s standard bearer against Obama.

“What you have with me is ‘what you see is what you get,’?” Santorum said, “as opposed to ‘what you see today may be something different than what you get tomorrow.’?”

Santorum is likewise preparing to fight on for weeks or months, enticed by new party rules that award delegates in early primaries and caucuses based on each candidate’s share of the votes. “The race is going to go a long time,” he promised as he left the stage.

That system is a major contributor to the prolonged nature of the contest, along with the advent of supportive and well-financed super PACs that have helped Romney’s competitors stay in the delegate hunt when their candidacies might otherwise have withered without enough cash.

Still, for many Republicans, the question is not just whether Romney will eventually capture the nomination, but at what cost?

Party concerns

There is a growing sense among party leaders that the primary fight has gone on long enough and that continued attacks by the candidates and their allies on one another could damage the party’s prospects in the fall. Being on both the giving and receiving end of the negative campaigning threatens to dent Romney’s prospects in particular in a general election, some Republicans said.

“It’s important for the candidates to recognize that they have to appeal to primary voters and not turn off independent voters that will be part of a winning coalition,” former Gov. Jeb Bush of Florida told reporters last week. Bush, who is frequently mentioned as a possible late entrant into the race, added, “It’s a little troubling sometimes when people are appealing to people’s fears and emotion.”

Even as Santorum appealed to conservatives for support in Michigan on Saturday, his allies were already advertising on his behalf in the next round of states to vote, another indication of how the candidates are planning to keep trading punches no matter what the outcome is on Tuesday.

The acknowledgment that the intraparty competition will most likely continue into the spring would seem to sweep aside the Romney campaign’s hope that it could string together a series of early victories sufficient to claim the nominee’s mantle — symbolically, at least — and begin focusing exclusively on Obama.