The Rand Paul–Mike Lee policy partnership has been the most important Republican collaboration in Washington in recent memory. They have tried subtly — and sometimes not so subtly — to change the Republican brand by applying conservative and libertarian principles differently than the party has in the past.

The two Tea Party senators have worked together on civil liberties, opposing the Patriot Act, attempting to rein in the National Security Agency, speaking out against extrajudicial killings of American citizens, protesting warrantless searches, and trying to strip indefinite detention from the National Defense Authorization Act.

Paul and Lee have also taken the lead on sentencing reform, seeking to correct excessive and racially discriminatory sentences for nonviolent offenders. The pair, both elected in 2010 after beating establishment-backed Republican candidates, also support prison reform.

To a lesser extent, they have been allies on foreign policy. They support repealing the Iraq War authorization. They both opposed the war in Libya and a proposed military intervention in Syria. Lee appears to be more hawkish than Paul on Iran, however.

On their face, none of these policy initiatives are typically associated with the GOP. But all of them can be explained or defended on conservative grounds. And now, Paul and Lee are not alone.

Indeed, a new policy alliance has emerged between Lee and Marco Rubio. Rubio was also elected in 2010 after beating back the Republican establishment, but — save for the disastrous Gang of Eight immigration machination — didn't rock the boat too much once he arrived in Washington. Until now.

Lee and Rubio have worked together on what they describe as "pro-growth, pro-family tax reform." The broad strokes are consistent with supply-side economics, but the details are more focused on lowering tax bills for families with children rather than fixating on the top marginal income tax rate.

Rubio and Lee have similar ideas for using devolution to fix entitlements for the poor. They would send block grants to the states to fund many anti-poverty programs currently run by Washington. The two also talk about a bigger role for civil society.

Now, it's not as if these three senators are in lockstep. Rubio hasn't yet joined with Lee on seeking greater Bill of Rights protections in the war on terror. Paul hasn't joined his old friend in pushing a family-friendly tax code with an expanded refundable child credit. Paul prefers the flat tax.

In a speech at the Heritage Foundation last year, Lee reminded conservatives that when the next presidential election rolls around, Ronald Reagan's 1980 victory will be as long ago as D-Day was at that time. But Lee has decided to follow Reagan's model of trying to provide tangible benefits to middle-class families through limited-government means. He would reform federal labor law to allow more flex time and improve work-life balance, and he would loosen federal control of college accreditation to increase competition for "brick-and-ivy" universities.

While he hasn't endorsed the entirely of this agenda, Rubio appears to be moving in the direction of Lee's basic political insight: Instead of repeating Reagan's 1980 platform, they should repeat his example of trying to make conservatism accessible — and materially helpful — to non-ideological people.

Even these slight shifts are likely to provoke intraparty debates as the 2016 primaries draw closer. Libertarian-leaning Republicans don't much like the child tax credit, seeing it as irrelevant to economic growth at best and social engineering via the tax code at worst.

Some simply don't see tax breaks for families — a part of the Contract With America, expanded under George W. Bush — as being much different from subsidies to Solyndra. Others worry that a larger child tax credit would inevitably mean higher tax rates on work and investment, thereby inhibiting growth.

You don't have to agree with all of the aforementioned proposals to see how different the Republican Party would look if Lee's policy entrepreneurship with Paul and Rubio gained traction: Less identified with war, wiretapping, and mandatory minimum sentences; more identified with reforming government programs and cutting taxes for the non-rich.

That's a prescription for updating the Republican brand without moving to the left or abandoning core principles. And, with any luck, it might prove to be a prescription for winning elections.