If Mitt Romney wins the Republican nomination for president, he'll face the urgent task of inspiring the party's conservative core and rallying them to beat President Barack Obama.
Judging by his performances in the primaries and caucuses so far, and the challenge he faces next week, he's got his work cut out for him.
Even Republicans who think he'll be the nominee worry about whether he can generate the intensity required to beat the Democratic incumbent.
These party leaders and activists, from the states voting Feb. 28 and the most contested ones ahead in the fall, say Romney has made strides toward addressing this problem. But, they say, he needs to do more to convince the Republican base that he's running to fundamentally reverse the nation's course, not simply manage what they see as the federal government's mess.
"I think Romney will be the nominee, but there is still tremendous work to be done," said Sally Bradshaw, a Florida Republican and adviser to former Gov. Jeb Bush. "He has got to find a way to unify the party and increase the intensity of support for him among voters who have supported Newt Gingrich, or Rick Santorum or Ron Paul or someone else. And that is going to be the key to how he does in the fall."
Romney leads in the delegate count for the nomination, and by a wide margin in private polling ahead of the Arizona primary Feb. 28. But the rising challenge from former Pennsylvania Sen. Rick Santorum in the contest also that day in Michigan, where Romney was born and raised, underscores doubts about Romney's ability to ignite fervor in the GOP base.
He nearly tied Santorum in Iowa, although entrance polls showed that more of Santorum's backers than Romney's said they were strongly behind their chosen candidate.
Romney lost the primary in South Carolina last month to former House Speaker Newt Gingrich. More of Romney's supporters in that state said they would support him with reservations in the general election than would support him enthusiastically.
Santorum swept caucuses Feb. 7 in Colorado and Minnesota, and the nonbinding Missouri primary.
Romney's challengers have risen by sounding more conservative and displaying sharper differences with Obama, while nipping Romney's appeal as the most electable against Obama.
Romney, a former Massachusetts governor with a moderate past, has campaigned more as the likely GOP nominee, portraying himself as acceptable to swing voters in a race where polls show voters prizing most a candidate's perceived ability to beat Obama.
Romney has pivoted toward the GOP's conservative base in light of Santorum's surge.
He dove into the debate over whether birth control ought to be covered by health insurance provided by church-backed employers by faulting the Obama administration's original push to do so as an "assault on religion." But Romney was accused of overreaching after recently telling influential conservative activists, "I was a severely conservative Republican governor."
"In Romney's case it's like the difference between someone who grew up speaking Spanish and someone who went to school to speak Spanish," said Constantin Querard, an Arizona Republican operative. "The moment Romney starts speaking, people know the difference."
A Pew Research poll taken last week shows the Republican voters nationally who think Romney is a strong conservative has dipped to 42 percent from 53 percent in November.
Romney's campaign aides say it's unrealistic to think conservatives staring at the possibility of a second Obama term will not unify behind Romney. "President Obama is the best unifier the Republican Party could ever hope for," Romney's political director, Rich Beeson, told The Associated Press.
The campaign points to recent conservative opinion leaders who have signed on to his campaign, and his support from popular rising conservative figures such as South Carolina Gov. Nikki Haley as evidence of Romney's newfound buzz.
Michigan Republican Holly Hughes, who supported Arizona Sen. John McCain in the 2008 primary, said Romney is more passionate than during his failed bid that year.
"He's a different candidate than he was four years ago," said Hughes, a Republican national committeewoman from Muskegon County. "There wasn't the excitement there."
Hughes and others also point to Romney's winning the straw poll at the recent Conservative Political Action Convention in Washington, which attracted thousands of the nation's most ardent conservative activists.
Yet Michigan GOP consultant Tom Shields said Santorum, now ahead of Romney in polls Romney's native state and where his father served as governor, is exciting people where Romney isn't.
Establishment Republican figures are lining up behind Romney in Michigan, including Gov. Rick Snyder. But in 2000, Gov. John Engler promised to deliver the state as George W. Bush's firewall; McCain won the primary that year.
"For whatever reason, Romney's not objectionable. But people just haven't fully warmed up to him," said Shields, who conducts public opinion polling in Michigan. "They've just refused to take the next step and marry the guy."
It foretells problems assuring the die-hard GOP activists will be lining up in November, when their phone-banking and door-knocking could make the difference in a close election against an Obama re-election campaign projected to have $1 billion to spend.
"I voted for him. I don't want to screw around because he's who we're going to end up with," said former Arizona GOP Chairman Mike Hellon, referring to his absentee primary vote for Romney. "But I talk to people who are generally reluctant to pull the trigger for him. More than anything else, that's' a problem of intensity which could be a problem in the fall."
Romney could spice things up with his running-mate choice, although some say an August announcement might be too late to lock in the GOP foot-soldiers.
"There's a lot of speculation that Marco Rubio could be the vice presidential nominee," Iowa Gov. Terry Branstad told the AP, referring to the freshman Florida senator and tea party favorite. "I think somebody like him could add some real excitement to the ticket, would be kind of a help to Romney if he does wrap up the nomination."
Candidates historically do not win close elections based on their running mate, although they have in recent elections received a temporary bump in their national poll standing. The choice can ignite passion among the party base, as did McCain's selection of Alaska Gov. Sarah Palin in 2008.
Concerns about the enthusiasm Romney generates correspond with a general dip in excitement among Republicans in a nominating campaign that has lurched one way and another in nine contests over the past six weeks.
A CNN/ORC International poll published Wednesday showed 51 percent of Republicans nationally were extremely or very enthusiastic about voting for president in the election, down from 64 percent in October.
But the dip in GOP enthusiasm, and especially Romney's three-way loss this month, is a stark warning to Romney that he cannot wait or rely on public unpopularity with Obama to provide momentum for him.
"He cannot bank on the anger against Obama among Republicans to create the turnout we need in the Fall," Florida's Bradshaw said.