Mitt Romney has tapped Wisconsin Rep. Paul Ryan to be his running mate, the campaign confirmed Saturday morning. 

The Romney campaign formally announced the selection via its mobile-phone app. An alert that crossed shortly after 7 a.m. ET said: "Mitt's Choice for VP is Paul Ryan."

Word had already gotten out that the Republican presidential candidate had chosen the seven-term congressman and budget policy guru as his running mate. Multiple sources with knowledge of the decision confirmed the choice to Fox News early Saturday. 

Romney will make the selection official during a campaign stop Saturday morning in Norfolk, Va., before launching his "The Romney Plan For A Stronger Middle Class" bus tour. Romney is expected to speak at about 9 a.m. ET. 

The selection comes roughly two weeks before the start of the Republican National Convention in Tampa, and gives Romney plenty of space to rally the party behind his pick before the official nomination.  

The announcement comes as some polls, including a recent Fox News survey, show the Republican presidential candidate losing some ground to President Obama.

Ryan, 42, already considered a rising star in the Republican Party, is chairman of the House Budget Committee. He’s been in Congress since 1999 and is best known this session for his controversial budget plan that includes an overhaul of Medicare.

Democrats have persistently tried to vilify that plan as a scheme to “end Medicare as we know it.”

But Ryan, a bookish but telegenic lawmaker, has stuck by his proposal as the solution to an ever-growing deficit inflamed by out-of-control entitlement spending.

Ryan has made fiscal discipline the touchstone of his tenure on the budget committee. With Ryan at his side, Romney can focus on jobs-creation proposals while his running mate focuses on plans for balancing the government’s books.

Romney was the youngest member of his freshmen class when he entered Congress in 1999 at age 28. He had served as a congressional aide before that. 

Ryan still lives in his hometown of Janesville, Wis., with his wife and three children.