It's clear that Vice President Joe Biden and Rep. Paul Ryan want the No. 2 job. But why?

After all, the vice presidency hasn't always been a coveted office. At the dawn of the republic, it was a constitutional consolation prize: the vice president was the person who finished second in the Electoral College.

Few of the 47 vice presidents in American history are noteworthy. Don't worry if you haven't heard of Hannibal Hamlin or Richard Mentor Johnson. In fact, most VPs prior to the 20th century are memorable because either they became president or shot Alexander Hamilton.

Constitutionally, the vice president's role amounts to presiding over the Senate and casting the tie-breaking vote, opening the electoral votes, and becoming president if his predecessor dies, resigns, or is "incapable of discharging his duties."

FDR's first Vice President John Nance Garner summarized these duties more poetically as "not worth a bucket of warm (spit)." And yet, buckets aside, the vice presidency is more today than it used to be.

Early VPs had little to do in the executive branch. They kept an office on Capitol Hill and presided over the Senate. They neither attended Cabinet meetings nor crafted policy.

But this changed in the 20th century. First, as Harold C. Relyea reveals in "The Vice Presidency: Evolution of the Modern Office, 1933-2001," there were meetings to attend and even chair. As the first president to go overseas, Woodrow Wilson relied on his vice president, Thomas R. Marshall, to chair the Cabinet meetings in his absence.

Beyond attending meetings, FDR's No. 2 men actively participated in Cabinet meetings, acted as liaisons to Capitol Hill, and traveled abroad in the president's stead. Truman's vice president (Alben Barkley) was the first to sit on the National Security Council. Richard Nixon took an even greater role in Cabinet meetings and councils.

All this changed when Vice President Lyndon Johnson established an office in the Executive Office Building next to the White House.

Then, in the 1970s Congress gave the vice president a budget to hire his own staff. Previously, VPs borrowed employees from other departments and agencies. Now, Gerald Ford had his own national security adviser and his own counsel. Walter Mondale added his own staff for domestic policy. Gradually, the vice president's staff mirrored that of the president's staff.

Soon, vice presidents started acting as if they were, in fact, in charge.

Proximity, staffing and personalities have made the office steadily more powerful. From Walter Mondale to Joe Biden, vice presidents not only kept offices near the boss and met routinely with him, they helped shape the policy agenda. They exercised their policy power through their membership on various policy commissions, councils, and task forces. Some, including Al Gore and Dick Cheney, had the president's ear and his trust.

The days of selecting a vice president simply because he or she is likely to deliver a crucial state's electoral votes are over. Obama, after all, would have won Delaware in 2008 no matter what, while George W. Bush had Wyoming's three electoral votes sewn up far before Cheney joined the ticket.

Paul Ryan follows this trend. He may help Romney carry Wisconsin, but what he really brings is legislative experience and policy ideas. He's an intellectual force in the U.S. House of Representatives. His budget, "The Path to Prosperity," which the House passed earlier this year, is a blueprint for spending and entitlement reform.

Biden, for his part, touted foreign policy experience Obama lacked in 2008. While in office he's been asked to oversee the implementation of the stimulus spending.

The vice president is now a policy driver. That's a good thing, because America is at a crossroads. The winner of this election can either help guide the country even further along the road to progressivism, or help it begin a long, slow turn back toward the principles of the American founding.

This is the country's choice. The ensuing debate over that choice and our options will allow the American people to determine their own future. The cast of characters is set. Let the debate continue.