FILE - In this Sept. 24, 2011, photo, Republican presidential candidate Texas Gov. Rick Perry addresses the Republican Leadership Conference at the Grand Hotel on Mackinac Island, Mich. He calls his rivals “heartless” and defends moderate parts of his immigration record with ethnically charged language. But Perry’s strategy may endear the Texas governor to Hispanics even as it angers others the presidential candidate must woo to win. (AP Photo/Carlos Osorio, File) The Associated PressWASHINGTON (AP) — Super PACs are like shadow cash machines for presidential candidates, and they're going to be big this year.The independent fundraising groups can gather and spend unlimited money to run ads supporting their candidate or attacking a rival. Mitt Romney and Rick Perry are the leading Republican contenders, and both have at least one super PAC. Another one is backing President Barack Obama's re-election bid.Super PACs aren't permitted to coordinate directly with the campaigns, which must follow strict federal restrictions on what they can raise and spend. Former aides and fundraisers who know the candidates' thinking and strategies staff many of the groups.Watchdog groups see super PACs as just the latest erosion of campaign finance rules that date to the Watergate era.