(Image Credit: Scott Olson/Getty Images)

Despite his no longer being a presidential candidate and having yet to endorse the presumptive GOP nominee, Rick Santorum gave an impassioned address to the National Rifle Association's annual meeting today in St. Louis and implored the attendees to "make sure we defeat Barack Obama in the general election."

Santorum ended his bid for the presidency earlier this week and noted his appearance as a former presidential candidate is different than when he originally agreed to speak.

Both Mitt Romney and Newt Gingrich addressed the convention before Santorum and he only mentioned Romney once when he said he agreed with his former rival's comments on the future of the Supreme Court being at stake in the election.

But he made a full-throated argument that Obama must be denied re-election, without mentioning Romney's name, calling it, as he did throughout his presidential campaign, "the most important election of your lifetime."

"The reason I drove around Iowa in a pickup truck with a guy named Chuck for months on end with no chance of winning is because Karen and my family thought we had to be all in," Santorum said, recalling his time in Iowa being driven around in volunteer Chuck Laudner's truck. "This was not a race that I felt comfortable sitting on the sidelines, so I ask all of you to do everything you can."

He then told the audience that he knows there will always be candidates that aren't perfect, a seemingly subtle reference to Romney, but "we've got to win."

"We've got to elect conservatives in our primaries and make sure they are elected in the general election, but we have to be all in," Santorum said, referring to NRA executive vice president Wayne LaPierre's earlier address. "I pledge to you I will be all in from now until November. I will do everything I can to elect Republicans up and down the ticket and with your help we, will do it."

The former Pennsylvania senator, 53,  also noted that his wife, Karen, was also supposed to join him at the convention, but was home in Virginia with their 3-year-old daughter, Bella, who is still recovering from a bout of pneumonia that took her to the hospital last weekend before he ended his campaign. Bella suffers from Trisomy 18, a rare genetic disorder. He said his wife is a passionate gun owner who "owns way more guns than I do" and said daughter Bella, as of today, is also a life member.

"Karen and I are life members of the NRA and we wanted to announce today that … Bella is a life member of the NRA, too. And I hope it's a long life," Santorum said to cheers.

Although Santorum spoke minutes after Romney and the two are expected to meet to discuss  an endorsement in the near future, such a meeting did not take place today in St. Louis. The two might meet next week when Romney campaigns in Pennsylvania, but it's just as likely they will not meet until after the Pennsylvania primary April 24, sources said.

New York, Connecticut and Delaware also vote that day.