The last days of the 2012 presidential election are a study in contrasts. Barack Obama has chosen to end his final campaign with an appeal both sour and small — Big Bird, binders and Romnesia. It is little wonder that Mitt Romney’s personal favorability rating now exceeds the president’s. Obama’s closing message is remarkable for its aggression, mocking tone and sheer triviality.

The Romney campaign is ending larger than it has been. Romney has used his final weeks to position himself — his critics would say reposition himself — as a moderate conservative, dedicated to bipartisan progress. Obama attacks Romney as a chameleon for refusing to be a caricature. Romney — admittedly a bit late — sets out a centrist governing philosophy. Both candidates, revealingly, are mainly talking about Romney.

Paul Ryan’s recent speech at Cleveland State University was an important part of the Romney campaign’s “go large” strategy — a presentation on political philosophy amid the normal stump speeches. Following a Republican primary season heavy on tea party rhetoric and a GOP convention light on substance, Ryan outlined a conservative vision of the common good.

Those who expect Ryan to sound like Ayn Rand — an embarrassing past flirtation — got something very different. Ryan quoted Abraham Lincoln on social mobility — “an unfettered start and a fair chance in the race of life.” Ryan identified with his old mentor Jack Kemp: “When he spoke of progress, he meant progress for everyone.” And without quoting him, Ryan embraced Pope John Paul II’s emphasis on the importance of healthy civic and religious institutions. It is a combination — Lincoln, Kemp and Catholic social thought — that must have set Rand aspinning.

At the same time, Ryan managed to probe one of Obama’s sore spots — the fact that he presides over the highest poverty rates in a generation. This state of affairs is enough to embarrass any self-respecting Democrat, so Obama avoids the topic. Ryan reintroduced it. He also correctly diagnosed America’s main social challenge — stalled mobility. “There is something wrong in our country,” argued Ryan, “when 40 percent of children born to parents in the lowest fifth of earners never know anything better. The question before us today — and it demands a serious answer — is how we get the engines of upward mobility turned back on.”

Ryan’s answer was serious without being comprehensive. He was strongest on the need for education reform in mediocre schools that routinely betray poor and minority children. Ryan correctly criticized welfare policies that encourage dependence and undermine family commitments. But he had less to say about the decline of decent paying, blue-collar jobs, which consigns many communities, in places such as Ohio, to economic and social decay.

Ryan’s main contribution in the Cleveland speech was to fill out a positive Republican governing philosophy. The speech recognized that equal opportunity is not a natural state. Rather, it is a social achievement — “something we’ve had to constantly fight for.” And Ryan defined a sophisticated division of labor between government and civic institutions in promoting opportunity: “There has to be a balance — allowing government to act for the common good, while leaving private groups free to do the work that only they can do. . . . Our families and our neighborhoods, the groups we join, our places of worship . . . this is where we live our lives. They shape our character, they give our lives direction, and they help make us a self-governing people.”

Ryan was particularly effective in critiquing the Obama administration’s threats to this delicate social ecosystem. Excessive government debt, he said, “crowds out civil society by drawing resources away from private giving.” The abuse of federal power — particularly the contraception mandate placed on religious charities and hospitals — undermines the humane partnership between government and civil society and weakens the safety net.

The speech had gaps. I would have preferred a more specific assurance that government retrenchment will not come at the expense of the poor and vulnerable. Cutting a middle-class entitlement is not the equal of cutting an AIDS program. The religious institutions Ryan rightly praised in his speech would doubtlessly remind Romney and Ryan of a continuing need for moral discernment in a time of austerity.

But Ryan has done something important. He has provided a Romney administration with a domestic policy approach — the promotion of social mobility — that is consistent with conservative principles while appealing to the good heart of a nation.