Representative Paul Ryan, R-Wis., called the troubled ObamaCare rollout an example of the "hollowness of big government" in his first appearance in Iowa since the 2012 presidential election.
Ryan, the GOP nominee for vice-president last year, addressed a crowd of around 800 Republican stalwarts as the featured speaker at a birthday fundraiser for Iowa Gov. Terry Branstad.
While the audience in the packed ballroom in Altoona dined on barbecued pork and fried chicken, Ryan repeatedly praised Branstad for enacting tax cuts this year with a politically divided legislature, calling it "an example people in Washington can learn from."
Branstad also praised Ryan, calling him "a common-sense statesman from a neighboring state that's really trying to do the right thing."
But Ryan devoted most of his address to hammering the botched rollout of President Obama's signature healthcare law.
"Remember we were told we had to pass this bill to find out what was in it," Ryan said. "Well, here we are."
The eight-term congressman added that there were only two explanations for the problems plaguing ObamaCare: "Either [the Obama administration was] being dishonest, or they are incompetent I don't know which is worse.
"You don't shut out opposition, you don't cram bad bills into law, you don't say one thing when you know it's another, and then when it all blows up in their face, saying 'I'm sorry' doesn't cut it."
Later in his speech, Ryan said Republicans "have to show we're not the opposition party, but that we're the proposition party" and hinted at his status as a possible candidate for the Republican presidential nomination in 2016 by saying "Maybe we should come back and do this more often.
The GOP ticket of former Massachusetts governor Mitt Romney and Ryan failed to carry Iowa in the 2012 general election. The state has not gone Republican since 2004.
Ryan was not the only possible presidential candidate speaking Saturday night, as Maryland Gov. Martin O'Malley, a possible Democratic contender, headlined the New Hampshire Democratic Party's Jefferson-Jackson dinner in Manchester.
O'Malley, a former Mayor of Baltimore, promoted himself as a can-do politician who criticized a political environment with "a lot more excuses and ideology than cooperation or action," adding "Enough finger-pointing. Enough obstruction. Enough wasted time."
The Associated Press contributed to this report.