Santorum after losses: 'It's halftime'

(CNN) - Despite disappointing finishes in all three of Tuesday's Republican primaries, Rick Santorum indicated no sign of letting up in his quest to win the Republican presidential nomination.

"The clock starts tonight," Santorum said to supporters in Pennsylvania.

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Speaking on familiar turf, the former two-term senator from the Keystone State urged supporters to dismiss attacks from his opponents ahead of Pennsylvania's primary later this month.

"You know me. You know how hard I work," Santorum said. "They'll say all the things, that I'm someone who doesn't stand up for what I believe in. You know me."

In recent days, Santorum has predicted he will win his home state's contest, which has 72 delegates at stake. He also expects to push on through May, a month that holds contests in what he deems more conservative states.

"We have now reached the point where it's halftime," Santorum said. "Half the delegates in this process have been selected, and who's ready to charge out of the locker room in Pennsylvania for a strong second half?"

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