Joining his father, U.S. Rep. Ron Paul, R-Tx., on the Republican presidential campaign trail, U.S. Sen. Rand Paul, R-Ky., ripped Rick Santorum and Mitt Romney as too liberal to defeat President Barack Obama in a general election.The father and son duo are on the trail in Iowa, where Congressman Paul has surged and is considered a "rock star" for his libertarian views. According to the final poll released by the Des Moines Register, Congressman Paul is statistically tied with Romney and could pull of an upset.Campaigning in Iowa, Sen. Paul pulled no punches about his father's opponents.From Politico (h/t PageOneKentucky): On CBS’s “The Early Show,” Sen. Rand Paul (R-Ky.) said of Santorum, “On economic issues, like foreign aid — he’s voted for foreign aid repeatedly, he’s voted to double the size of the Department of Education. Old-school Reagan Republicans don’t believe in the Department of Education — Rick Santorum voted to double the size of the Department of Education.” Moving on to Mitt Romney, the Kentucky senator said the former Massachusetts governor, too, would not be strong enough to beat the president. "He supported the linchpin of ‘Obamacare’ — the individual mandate — and he supported the bank bailout," he said. “All of these things wrapped together don’t make Romney a good opponent for Obama, either."