House Budget Committee Chairman Paul Ryan, R-Wisc., endorsed Mitt Romney for the Republican presidential nomination Friday.

Ryan is regarded as an up-and-coming Republican star, and is considered the party's leading expert on how to shape a budget that's sensitive to conservative ideology. The House, on a largely party line vote, passed his budget Thursday; it's likely to go nowhere in the Democratic-run Senate.

Ryan's endorsement also carries some weight because his state's voters go to the polls Tuesday in a closely-watched primary.

Here's some of Ryan's comments about Romney Friday morning:

"I have two criteria I’m using to make my decision to vote in our primary on Tuesday. Who is the best person to be president? Who will make the best president? And who has the best chance of defeating Barack Obama? In my opinion, Mitt Romney is clearly that person," Ryan said.

"Here’s the other point: I spent a good deal of time with Mitt Romney and his staff recently going through our country's fiscal situation, talking about just what it’s going to take to get the country back on track. And I am convinced that Mitt Romney has the skills, the tenacity, the principles, the courage and the integrity to do what it takes to get America back on track."

Ryan also said the ongoing battle for the GOP nomination has "been constructive up 'til now. I think it's made the candidates better. But I think we're entering a phase where it could become counterproductive if this drags on much longer. And so that’s why I think we need to coalesce as conservatives around Mitt Romney and focus on the big task at hand which is defeating Barack Obama in the fall.”