The business marketer noticed how plainly they talked about the nation’s mounting deficit problems. The boat parts supplier came away convinced that together they could fix the economy. The pharmacy clerk, well, she observed how when each of them spoke, the other was smiling — a kind of respectful smile.

And after seeing Mitt Romney and Paul Ryan trade compliments, banter about the Boy Scouts and take turns talking taxes and debt, these three Wisconsin Republican voters arrived at the same conclusion: This could be the ticket.

If Romney’s win in Wisconsin strengthened his claim to the Republican presidential nomination, then his five straight days of campaigning with Ryan amounted to a tryout for the youthful congressman as a potential vice presidential running mate.

Since Ryan endorsed Romney last Friday, he was at the candidate’s side at every turn — introducing him before formal speeches, vouching for him at town hall meetings and joining him as they eyed cherry pie, picked up fried cheese curds and handed out sub sandwiches. (Romney gave away turkey; Ryan, ham and cheese.)

Along the way, Romney’s aides were sizing Ryan up. And although chief strategist Stuart Stevens waved off any talk of the two forming a national ticket as irresponsibly premature, he did say they got along well behind the scenes and noted their “chemistry” on the stump.

To some Republicans, Ryan’s positive attributes are obvious. Where some conservatives see Romney as an ideological squish, they consider Ryan not only a conservative of conviction but one of the movement’s intellectual champions. Where Romney, 65, is a private equity patrician from Boston, Ryan, 42, spent his teenage years living off Social Security benefits in blue-collar Janesville after his father died prematurely of a heart attack.

All year, Romney has struggled to connect with working-class voters, but Ryan showed how he might help as he introduced Romney at a forum Saturday in Pewaukee. Ryan talked casually about having been on “a road to opportunity” when he flipped burgers at a McDonald’s as a teenager, sold bologna — “real bologna, by the way” — for Oscar Mayer and waited tables to help pay back his student loans.

“Anybody fill up gas lately?” Ryan asked. “I mean, I filled up my truck last night and I couldn’t even get it to full because it cut me off at $100 — the credit card wouldn’t even let me buy any more gas. It’s ridiculous.”

The Romney-Ryan road show did more than stoke the “veepstakes,” Washington’s favorite quadrennial parlor game, however. It also cemented Romney’s embrace of Ryan’s controversial agenda as chairman of the House Budget Committee.

President Obama made clear in a speech Tuesday that he would campaign for reelection against Ryan’s budget proposal and tie Romney to it. Labeling the plan “radical,” Obama said it would pit the poor against the wealthy in a form of “social Darwinism.” The president also mocked Romney for having called the proposal “marvelous.”

On the campaign trail here, Romney has alternately called Ryan “a great leader,” “a wonderful speaker” and “a great man.” After Ryan endorsed him Friday in Appleton, Romney said: “This is a guy who’s willing to stand for something. He didn’t just go to Washington to be seen and to have a little job there. He went to Washington to make a difference.”

Since then, their chemistry seemed to grow. By Sunday, Ryan was scheming with the campaign’s advance staffers to orchestrate an elaborate prank on Romney.

They ushered Romney into a ballroom for a pancake brunch. As Romney waited backstage behind a black curtain, Ryan introduced him with customary enthusiasm — “the next president of the United States!” Romney could hear the crowd applaud. When his intro song, Kid Rock’s “Born Free,” started playing, he emerged from behind the black curtain.

Only the room was empty, save for a few staffers filming it all on their iPhones, and the applause was merely a soundtrack.

April Fools!

Later that day, it was Romney making the jokes. “This guy here, this is not my son,” he told one crowd in Middleton, poking fun of Ryan’s relative youth. Addressing another audience, he joked that Ryan was only 10 years old when Ronald Reagan ran for president in 1980.

“I did have a Reagan bumper sticker on my locker in the third grade,” Ryan offered.

“This guy was born conservative!” Romney quipped.

By Monday afternoon, at a town hall meeting in Milwaukee, Romney was content to let Ryan answer questions on his behalf. When a voter asked Romney to explain his plan to simplify the tax code, he responded: “I heard the congressman answer this question better than I can last time we chatted, so I’m going to have him describe, just for a moment, his plans on the tax code, which are very similar to my own.”

And this is when Sherry Magner, the pharmacy clerk, decided who she thinks Romney should pick as his running mate.

“I thought the chemistry was really great between the two of them,” Magner, 61, said. “I was watching each one as the other spoke, and there was not only respect, but a smile they gave each other.”

Added Jeff Burns, 54, the boat parts supplier, who was also in the audience: “This election’s gonna turn on the economy and you’ve got two guys who know what it takes to fix the economy. You’re talking about a very successful businessman and the most knowledgeable congressman available.”

So if Romney does end up selecting Ryan — and it is a big if; Romney says he hasn’t even begun considering a short list — there’s one more thing they have in common: an uninhibited passion for patriotic songs.

Romney spent weeks on the campaign trail this year reciting the lyrics to “America the Beautiful.” At a rally one January night in The Villages, Fla., he was so moved that he actually broke out in song.

But Ryan, apparently, beat him to that feat.

On a family hiking trip near Colorado’s Snowmass peak, according to an account in the Milwaukee Journal Sentinel, 6-year-old Ryan took in the mountain vista and spontaneously sang, “America the Beautiful.”

“We’re all there looking at each other smiling at this kid capturing the moment,” Ryan’s older brother, Tobin, told the newspaper. “I think there was something in his genetic makeup.”