Clinton has used her seven years in the Senate to begin rehabilitating her reputation as one of the most polarizing figures in American politics and the architect of a failed healthcare plan. Obama's brief tenure has allowed him to establish himself as a national figure in a way he never could have as a mere Illinois state legislator.
They took divergent approaches to their Senate careers, however. And their strategies reflected both their own political needs and the distinctive ways they tackle challenges -- differences that could ultimately make them very different presidents.
Clinton chose to build a reputation as a skilled insider: She mastered the levers of Senate power, developed a record of delivering for her state, and proved she could work effectively with diverse colleagues -- including Republicans who had demonized her as first lady.
Obama cast himself as more of an outsider: He challenged some of the Senate's treasured ways of operating -- especially in the field of ethics. At the same time, he bulked up the foreign policy credentials he would need to run for president and cultivated the profile of a "post-partisan," reform-minded politician.
The contrast between the candidates' approaches to the Senate mirrors the choice now facing Democratic primary voters -- between Clinton's emphasis on competence and kitchen-table issues, and Obama's focus on broad themes and overarching issues.
But it does more than foreshadow campaign strategy. It gives voters an unusual glimpse into the kinds of presidents they might turn out to be.
Their Capitol Hill tours have not been without political risks. The Senate has a tradition of giving the cold shoulder to newcomers who arrive with glittering reputations and outsized ambitions but fail to defer to senior members. Even the appearance of failing to succeed in the Senate could have damaged Clinton's and Obama's White House chances.
Neither Clinton nor Obama can claim credit for groundbreaking legislation. They have partly been hampered by their relatively short tenure and by the fact that Democrats were in the minority until 2007. If major bills with a candidate's name on it were the best test of leadership, Sen. John McCain (R-Ariz.) would win hands down: He has top billing on major campaign finance, immigration and global warming measures.
Clinton and Obama each arrived in the Senate in a spotlight. They were being asked if they planned to run for president even before they were sworn in.
Clinton was one of the best-known women in the country; Obama's keynote speech at the 2004 Democratic Convention had brought down the house, and his memoir of his early life was a bestseller.
In a sign of the buzz over his 2005 arrival, Obama soon after was invited to don a tuxedo and speak at a dinner of the Gridiron Club, an insiders' press event.
"I am so overexposed, I make Paris Hilton look like a recluse," Obama joked. The challenge was to show that he had substance too.
She keeps her head down
Clinton's challenge was different: A decade-long national reputation preceded her, but she was loathed by many Republicans as the embodiment of liberalism and the face of socialized medicine because of her role in President Clinton's ill-fated healthcare plan.
Members of both parties feared she would be a prima donna and treat the Senate as a mere springboard to the White House.
Clinton surprised her colleagues with her diligence and deference. One of the earliest examples of her strategy involved fellow Democrat Robert C. Byrd of West Virginia, the most senior member of the Senate.
Not long after she won her seat in 2000, the former first lady approached Byrd as a humble student seeking lessons in the arcane ways of the tradition-bound institution. It was a gutsy gesture, because the powerful Senate elder had been openly hostile to President Clinton after his scandalous dalliance with a White House intern.
After a series of private tutorials, Sen. Clinton won Byrd as an ally. Months later, after the Sept. 11 attacks, he helped her secure $20 billion in aid for her state. "Count me in as the third senator from New York," he said.