STEUBENVILLE, Ohio (AP) — Republican Rick Santorum says "this was a big night tonight" and is calling the day's biggest race in Ohio "too close to call."Santorum on Tuesday told supporters that "we're going to win a few and we're going to lose a few." But he delivered his remarks in a congressional district where he didn't appear on the ballot, underscoring the challenges facing his ragtag campaign.Santorum was heavily outspent by his rivals and he says his campaign "went up against enormous odds." He says he overcame obstacles and vowed to continue his campaign to defend liberty.Santorum won contests in Tennessee and Oklahoma and was running close behind Mitt Romney in Ohio, the biggest medal among the 10 states going to the polls on the campaign's biggest day so far.