Washington (CNN) -- With his budget approved by the House, Paul Ryan is turning his attention to Iowa to headline a high-profile Republican event that will only fuel speculation he's laying the groundwork for a potential presidential run in 2016. 

Lawmakers approved the Wisconsin Republican's 2015 spending plan on Thursday. But there were notable conservative defections, making his appearance at Friday's Lincoln Dinner in Cedar Rapids more interesting. 

The question that confronts Ryan is whether his budget, dubbed the "path to prosperity," will help pave a path for him to compete in the early contest state in two years. Or will it prove a political liability when Republicans choose their next White House nominee? 

Ryan's role as the chief fiscal expert in the GOP is the main reason he was tapped as Mitt Romney's running mate in 2012, and remains his main calling card in a potential national campaign. 

Since Republicans took control of the House in 2010, top GOP leaders have deferred to the Budget Committee chairman to construct the party's blueprint to address the growing national debt. 

He has shepherded four budgets through the House and brokered a deal with Democrats last fall to avoid another government shutdown and possible default on the nation's credit limit. 

Ryan budget details 

Some say not aggressive enough 

But that resume has not won over some tea party groups who believe Ryan isn't' being aggressive enough about slashing the size of the federal government. 

The group of fiscal conservatives in the House introduced an alternative budget that balances the federal budget in four years, instead of the 10 years in Ryan's plan. 
Why?
his attention to Iowa to headline a high-profile Republican event 