Her experience. His charm and fundraising ability. His support among liberals, independents and black voters. Her hold on white female voters, low-income Democrats, and Latinos.
With energized Democrats facing a difficult choice between two historic, formidable candidates vying to be the nation's first black or first women president, some have suggested that the two join forces on a single Democratic "dream ticket."
Fresh from her victories in Ohio, Texas and Rhode Island, Sen. Hillary Clinton, D-N.Y., appeared on network morning news programs Wednesday and suggested that a joint ticket with Sen. Barack Obama, D-Ill., is a real possibility.
On CBS' morning program, anchor Harry Smith said to Clinton, "We talked to a lot of people in Ohio who said there really isn't that significant a difference between you two, and they'd like to see you both on the ticket."
"Well, you know, that may be where this is headed." Clinton said. "But of course we have to decide who is on the top of the ticket. I think the people of Ohio very clearly said that it should be me."
On a plane from Texas to Chicago Wednesday, Obama smiled wryly when asked about the possibility of a joint Clinton-Obama or Obama-Clinton ticket.
"You know, we are just focused on winning this nomination," he said. "That's my focus. And you know, I've said before I respect Sen. Clinton as a public servant. She's a tenacious opponent. I think it is very premature to start talking about a joint ticket … right now."
Obama minimized the importance of Clinton's victories. "We had won 12 in a row. She won two," Obama told ABC's Diane Sawyer Wednesday morning on ABC's "Good Morning America" -- not counting Clinton's third March 4 win in Texas.
"These were states that she had huge leads going into it, and we closed that gap, but we couldn't close it as much as we'd like," Obama told "GMA." "It's going to be very hard for her to catch up on the pledged-delegate count."
For her part, Clinton continued to hammer away at Obama's national security credentials, suggesting she's the best one who can take on Sen. John McCain, R-Ariz.
"This election now is not only between Sen. Obama and myself. It is, in the voter's mind, between one of us and Sen. McCain. I think that's why I did so well last night," Clinton said Wednesday on "GMA."
"I think national security is the issue against John McCain. I think it is not only legitimate, it's necessary to ask voters to determine who they would like to see as commander in chief," Clinton added. "Now it's a real choice, because we know who the Republican nominee is going to be, and I think voters are going to want someone who can stand up on that stage, toe-to-toe with John McCain."
Some Democratic strategists say Clinton's suggestion that she is open to a joint ticket is smart strategy.
With only a handful of primary contests left, the possibility of a joint ticket could win her some Obama supporters who have reservations about his candidacy.
Conversely, a joint ticket could reassure those who believe Obama has a better shot against Republican nominee McCain in the general election.
"It's a way for her to play at 'If you like Obama and you're a little bit worried about his experience, don't worry, you can vote for me and I'll pick him,'" said Joe Trippi, who was the chief adviser to former Sen. John Edwards in his 2008 bid.