Washington (CNN) -- Fresh off a big win in Louisiana, Rick Santorum insisted Sunday that Republicans are rejecting the premise that rival Mitt Romney has virtually locked up the GOP presidential nomination.
"Even though a lot of folks are saying this race is over, people in Louisiana said, 'No, it's not,' " Santorum said on the CBS program "Face the Nation" about victory in Saturday's Bayou State primary.
Romney maintained his more than 2-to-1 lead in delegates despite the Santorum victory, raising questions about whether the former Pennsylvania senator can prevent Romney from securing the nomination ahead of the Republican convention in August.
To Santorum, it all comes down to growing concern on the political right about whether Romney, a former Massachusetts governor, truly holds conservative beliefs he has declared during the GOP campaign or will revert to more moderate stances of the past once the nomination is secured.
Voters "still want to see someone who they can trust, someone who is not running an Etch A Sketch campaign but one that, you know, has their principles written on their heart, not an erasable tablet," Santorum told the CBS program, taking a shot at last week's gaffe by a senior Romney aide who said the campaign would reset like an Etch A Sketch for the general election against President Barack Obama in November.
The road ahead is a difficult one for Santorum, who is slogging it out in what has become a game of numbers to clinch the 1,144 delegates needed to clinch the nomination.
According to CNN's unofficial estimates, Romney has 568 delegates compared to 261 for Santorum, 137 for former House Speaker Newt Gingrich and 71 for Texas Rep. Ron Paul.
With 100% of the Louisiana precincts reporting, Santorum won handily with more than 91,000 votes or 49% of the vote, according to the Louisiana Secretary of State's unofficial tally. Romney picked up more than 49,000 votes or 27%, it said, while Gingrich got more than 29,500 votes or 16%. Paul captured more than 11,000 votes for about 6%.
The candidates get a break in the primary schedule, with the next contests on April 3 in Wisconsin, Maryland and the District of Columbia. Only Santorum had campaign events scheduled for Sunday, both in Wisconsin, which will be significant as a potential battleground state in November.
While Romney called Santorum on Saturday night to congratulate him on his Louisiana win, the two camps were already jockeying to spin the win.
"Rick Santorum is like a football team celebrating a field goal when they are losing by seven touchdowns with less than a minute left in the game," Ryan Williams, a Romney campaign spokesman, said in a statement.
Santorum's team countered with their own statement that said: "Louisiana voters overwhelmingly rejected Mitt Romney's push to press the reset button, because they know that we need a clear contrast to President Obama's disastrous policies."
On Sunday, Santorum laughed off the Romney camp's statement of the previous night, saying: "That's just a desperate campaign that has no message."
The big question remained whether Santorum's showing in Louisiana will matter, given Romney's huge delegate lead.
Pressure is mounting from mainstream Republicans for Santorum and Gingrich to drop out of the race so Republicans can coalesce around what many consider to be Romney's inevitable nomination.
Gingrich, who has won only two Deep South states so far, vowed Saturday to stay in the race until the Republican convention in Florida.
"This is clearly still an open race," Gingrich said late. "So, on behalf of the more than 176,000 Americans who have donated to Newt 2012, I will carry our solution-oriented campaign to Tampa."
Conservative Sen. Lindsey Graham, R-South Carolina, made clear Sunday that he expects Romney to be his party's nominee, even though he has yet to make a formal endorsement.
"I think the primary's over. Romney will be the nominee," Graham said on CNN's "State of the Union," adding: "I'm very comfortable with him ... he'll get to 1,144."
Santorum and Gingrich have run "phenomenal races," Graham said, but now was the time for Republicans of all stripes to work together to defeat Obama in November.
While Santorum agreed Sunday on the need for unity to defeat Obama, he rejected any contention that the race was over. Electing Obama to a second term would be "the end of freedom as we know it," Santorum said on CBS, but Romney would be "the worst candidate" to race Obama.
Voters were looking for a candidate "who can win the election because they have better ideas, not because they can pound their opponent into the ground with negative ads," he said in reference Romney's superior campaign funding and super PAC backing.
In particular, Santorum cited the the similarities between the 2010 federal health care reform law hated by conservatives and the earlier Massachusetts health care law passed when Romney was governor, calling the issue a major weakness of Romney' s candidacy.
According to Santorum, Romney will be unable to debate health care with Obama because both backed similar policies. Romney contends his program was only designed for Massachusetts and that he would seek to repeal the federal plan if elected president.
However, the health care issue continues to haunt him on the campaign trail.
Obama's senior adviser, David Plouffe, made sure to highlight the Romney-Obama link on health care during appearances on Sunday talk shows.
"Mitt Romney is the godfather of our health care plan," Plouffe said on the NBC program "Meet the Press," noting that now Romney was "running away from that."
In response, Romney spokeswoman Andrea Saul said Romney would repeal Obama's health care law if elected president, calling it a "federal government power grab that violates the rights of states to pursue their own health care solutions."
Another issue Romney can't shake is the Etch A Sketch comment by senior campaign adviser Eric Fehrnstrom to CNN last week.
Asked if Romney had weakened his general election support from moderates by aligning too closely with conservative views in the primary campaign, Fehrnstrom said Wednesday the campaign would "reset" for the November race.
"It's almost like an Etch A Sketch," Fehrnstrom said of the popular drawing toy. "You can kind of shake it up, and we start all over again."
Since then, both Santorum and Gingrich have made an Etch A Sketch a regular campaign prop, and Plouffe made a point of mentioning it Sunday, as did Democratic Sen. Chuck Schumer of New York.
"He can run but he can't hide" from his past support of health care reform, Schumer said of Romney on the CBS program, adding the issue would "just increase the view that he's the Etch a Sketch" candidate.
Graham, meanwhile, predicted on CNN that the federal health care law and the role of government will be the central issue of the general election.
"The vice president whispered to the president when they signed the bill two years ago, 'This is a big f-ing deal,' " Graham said of health care reform. "Well now it's become a big f-ing mess for the Democratic Party and the country as a whole."
CNN's Phil Gast, Gabriella Schwarz and Chelsea J. Carter contributed to this report.