President Obama and Vice President Joe BidenJoseph (Joe) Robinette BidenBiden slams Trump over golf gif hitting Clinton Overnight Tech: Equifax hit by earlier undisclosed hack | Facebook takes heat over Russian ads | Alt-right Twitter rival may lose domain Overnight Finance: CBO to release limited analysis of ObamaCare repeal bill | DOJ investigates Equifax stock sales | House weighs tougher rules for banks dealing with North Korea MORE on Friday appeared at their first joint campaign rally this year on behalf Delaware nominee Chris CoonsChristopher (Chris) Andrew CoonsRaising awareness about maternal health worldwide on National Bump Day Senate plans hearing for bills to protect Mueller Entering a new era of African investment MORE (D), lauding him and one another after two years in office.

The president and vice president presented a unified front for the audience in Biden's hometown of Wilmington and made the case that Coons's election is crucial to keeping their agenda moving forward.

"This guy has a backbone like a ramrod," Biden said while introducing Obama, adding that he has "a brain bigger than his skull and a heart to match both."

Obama took the stage to a hardy ovation from the crowd and said, "I've had to make a lot of decisions over the last 24 months ...The single best decision I have made was selecting Joe Biden as my running mate."

The president's comment happened to come after the White House dismissed speculation last week that Secretary of State Hillary ClintonHillary Diane Rodham ClintonBiden slams Trump over golf gif hitting Clinton Overnight Cybersecurity: Equifax hit by earlier hack | What to know about Kaspersky controversy | Officials review EU-US privacy pact Overnight Tech: Equifax hit by earlier undisclosed hack | Facebook takes heat over Russian ads | Alt-right Twitter rival may lose domain MORE, who ran against Obama in the 2008 Democratic presidential primary, could join his 2012 reelection campaign as his running mate.

Obama and Biden made the case for electing Coons to the Senate, saying it will help them continue to revive the economy in the two years between this election and the next.

"It's really important we keep this momentum going, and it's impossible to keep this momentum going without the United States Senate," Biden said. "When Chris Coons goes to the United States Senate, you will never, ever, ever wonder why you voted for him."

Obama urged Democrats to work hard to elect Coons, even though most polls show him leading his Republican opponent Christine O'Donnell by double digits.

"It is difficult here, and it is difficult across the nation," Obama said "I don't want anyone here taking this for granted. This is a tough political environment."

Obama and Biden did not make mention of O'Donnell, who has nearly single-handedly helped attract national attention to the race. O'Donnell shocked many by defeating nine-term centrist Rep. Mike Castle (R) in the GOP Senate primary, then raised questions about her personal background by making controversial statements about religion and sexuality.

Obama, however, did aim at Republicans, saying they opposed his agenda for pure political gain and would impede progress by instituting policies that failed in the past.

"You have to give them credit, in terms of short-term tactics it wasn't a bad strategy," he said. "In terms of what's good for the country it, uh, didn't work out so well."

Biden appeared to be within his element during his third appearance on behalf of Coons, who is running for his old Senate seat. 

The vice president noted that Obama loves to talk about his home state of Hawaii and his adopted hometown of Chicago, but said, "He would not be president of the United States today but for Delaware," noting that two of his top campaign advisers, Dan Pfeiffer and David Plouffe, hail from the First State.

"Dan Pfeiffer's mom and dad, we owe you big," Biden added.