Mitt Romney answered his last question from a voter three weeks ago, and just about every day since then, he has swept through towns across America like a whistling train conductor proclaiming, “All aboard.”

Out are 55-minute town hall meetings. In are 15-minute stump speeches at buffed-up rallies. There are rope lines and hot lights, giant flags and Secret Service agents with wires in their ears. The objective: appear presidential, avoid gaffes and convince Republicans that they have no reasonable option left but to rally around Romney’s winning candidacy.

That was the image he presented here Saturday night with his Nevada caucus victory speech. Hundreds of adoring supporters waved “Nevada Believes” signs as the candidate assailed President Obama. Yet the music playing as soon as Romney finished speaking — “A Little Less Conversation” by Elvis Presley — underscored his new don’t-ask-questions-just- get-on-board mantra.

As Romney solidified his front-runner status with back-to-back decisive wins in Florida and Nevada, his confidence — and caution — have been on stark display. He has pivoted from a retail campaign based on convincing people at his events that he has a command of the issues to a made-for-television spectacle where the people are simply props helping project an aura of momentum and inevitability to a national audience.

“You need to really start focusing on ‘I am your man, and I’m the guy that will move this party forward,’ ” said Lanny Wiles, a veteran advance operative on Republican presidential campaigns. “It gets down to crowd building and enthusiasm, but a lot of that [voter] interaction is gone. For right now, it’s about pushing this train down the track as fast as you can.”

This is a natural evolution for any presidential campaign. In the volatile 2012 sweepstakes, it marks an inflection point as Romney begins to claim the mantle of the presumptive nominee.

Although Romney’s avoidance of questions from voters helps prevent him from making unforced errors, it does pose a risk that voters may see him as too cautious, calculating and detached.

“I’d just like to hear how he’d respond, see if he’s quick on his feet. . . . How else are you going to find out how he feels about things that are important to us?” said Karon Cowan, 63, an accountant who is torn between Romney and former House speaker Newt Gingrich and attended Romney’s rally Saturday in Colorado Springs, Colo.

But other voters are more forgiving, saying they want to see Romney deliver a more practiced repartee.

“I really feel that the speech is their foundation, their philosophy, and that’s what they project,” said Tim Roeland, 47, a homeland security worker who saw Romney in Colorado. “You get an ad hoc answer, that may not capture what he really thinks.”

The last time Romney took audience questions, Jan. 13 in Hilton Head, S.C., he got two off-the-wall ones. A girl doing a science project on germs wanted to know how many hands he shakes and how often he washes his hands. (He said he washes regularly and uses Purell sanitizer, too, “just to make sure.”) And an older woman asked whether he believes in “the divine saving grace of Jesus Christ.” (He said he did.)

For a presidential candidate, there’s no place more comfortable than at a rally, delivering a rehearsed spiel before hundreds of people who won’t ask tough questions — or any at all — and instead clap and scream your name as if on cue.

“You’re safe, you’re steady, you don’t put your candidate in a place where there could be any kind of a pitfall, you stick with the themes that have worked with you so far until you see reason to change them — and I don’t see any reason,” said one Romney adviser who requested anonymity to discuss the campaign’s strategy.

Despite the trappings of his public appearances, Romney’s advisers reject the notion that he is campaigning as the presumptive nominee. Aides point out that states such as Colorado are much larger and more populous than Iowa and New Hampshire and the demand to see Romney makes more intimate town hall-style forums impractical.

“We get into bigger states, you’ll see more message events and rallies,” senior adviser Eric Fehrnstrom said. “It doesn’t mean we’ve ruled out other types of events. It does mean we’re looking at revving up our supporter base and becoming more focused in our communications.”

Where the campaign was linear when the candidates could camp out for a week at a time in the first five voting states, the battle from here on will be fought on multiple fronts at once — with two, three or 10 states holding contests on a given day.

It is unclear whether Romney can continue his winning streak through the trio of states voting on Tuesday — Colorado, Minnesota and Missouri. He has not campaigned in Missouri, and several Romney advisers said privately that they consider Minnesota, where public polling has been inconsistent, to be up for grabs. They view former senator Rick Santorum (Pa.) as a strong threat in Minnesota and attacked him Sunday for the first time in a few weeks.

Romney campaigned last week in Eagan, Minn., but canceled a planned trip back to the state on Monday to instead spend time in Colorado, where he has a more robust operation.

At his campaign stops these days, Romney arrives in dramatic fashion. He emerges through a tunnel or steps off his logo-emblazoned bus, bounds on stage to loud rock music, looks out at the cheering supporters behind him, at his sides and in front of him and feigns shock at how many people have shown up.

In Colorado Springs on Saturday: “Wow!” In Reno, Nev., last Thursday: “What a welcome — what a Reno welcome!” In the Villages, Fla., last Monday: “Thanks, you guys. Wow!”

Romney then powers through his stump speech: President Obama doesn’t know how to lead, this election is about the soul of America, recite (or, if so inclined, sing) “America the Beautiful.”

“I love America’s hymns,” Romney said at the Colorado rally. “O beautiful for spacious skies, for amber waves of grain. When I was in Iowa, I said the amber waves of grain included corn, and I think that’s why I lost by 25 votes. You do have spacious skies here; no amber waves of grain that I know of.

“For purple mountains’ majesty,” he continued. “Oh, yes, you have those.”

Then Romney basks in the adoration of his supporters, shakes hands, poses with babies and heads for the airport to board his chartered Boeing 737. Another stop awaits.