I have to disagree.  Paul Ryan was authentic and stayed within bounds.  The speech may have been conservative, and you might not agree, but it did not breach any notable standards of credibility.  

Cronyism - was a clear reference to Solyndra; $500 million for someone with campaign connections to Obama

Obamacare... no place in a free country - echoes a recent Supreme Court's opinion:   the federal government cannot compel citizens to purchase something.

Raiding Medicare to hide the true cost - the Ryan Plan is a comprehensive package with many details;  you seem to be oversimplifying.

President Does Nothing - Ryan is asserting the deadlock was Obama's fault.  That's hard to gauge.  Ryan did make a detailed plan; it was passed by the House.   Obama never specified a detailed plan.  The detailed budgets Obama did specify were voted down unanimously even by Democrats.  Ryan's position appears reasonable.

Government planned / sanctimony - if President Obama's policies were carried to their logical conclusion, would we become a European welfare state?  When you consider that healthcare is 15% of our economy and the landmark bill of the past four years greatly added to government conrol over it, the breadth of Ryan's concern does have a basis.

In sum, Ryan has a strong viewpoint, and there is a foundation for all his comments.  We would expect no less from an analyst like Ryan.  He did not lose credibility.  To the contrary, he showed high integrity by taking political risk, and by speaking an uncomfortable and unpopular truth:  we have to stop spending money we don't have.

Paul Ryan has lied to the American people on the national stage in a blatant, offensive manner. He lied about the GM auto plant (it closed before Obama became president). He lied about "raiding Medicare" (and the same cuts are in his budget). He lied about the Simpson-Bowles bipartisan debt commission (he was on that commission, voted against it, and convinced others to vote against it - so, in fact, it never made any recommendations to the president). Ryan is a liar, and we are about to see Romney state some of the same lies.

I had to stop and write this when I came across the phrase "standard bearer for a man who wanted GM to go bankrupt". It is truly a sad day in journalism when the editorial page editor is so ignorant about basic facts, and simply repeats the talking points of the Democratic candidate. GM DID go bankrupt, and was assisted through it with billions of dollars of government help, which is likely never to be recovered. Romney did prefer that GM go through the standard bankruptcy process, from which it would have still emerged, but without the government losing billions. Canellos is proving why the Globe is no longer a serious source for news.

Thank you Peter for a shred of sanity. When he started with the whole "he did nothing" stuff I had to turn him off. What a complete pack of distorted bald face lies.

You want to see attacks, wait until next week, it will be quite a show.

For Ryan to accuse anyone else of sanctimony is laughable. 

This story reads like it was written by a representative of the Obama campaign. Dems have been using "mediscare" tactics for decades. Guess they don't like it when it is used against them.

I am very impressed with the comment by richmond12. He would be a better journalist than the author of this story.

Credibility? You want to talk about credibility. Sheesh! You say: "He attacked Obama for failing to keep open a General Motors plant in Wisconsin", which is pure mendacity. He criticized (note my use of the non-hysterical verb; if you ever work for a serious publisher, you will need to know how to choose adult language like that) Obama, not for failing to keep it open, but for failing to keep his phony promise - i.e. for lying.

Obama stood in that plant in 2008 and clearly led the people to believe that he, if elected President, would keep it open "for the next 100 years", using government leverage. Later, in June of 2008, he again said: "As president, I will lead an effort to retool plants like the GM facility in Janesville". It closed in April 2009. After Obama swept in and took over the company with federal tax money, re-opening the Janesville plant for another car line was considered, but the work went elsewhere. Another plant, in Spring Hill, TN, shutdown in November, but was later re-opened. What remains closed is Janesville, which is not only the plant where he made the promise to the workers, but also happens to be in his hated rival's (Ryan's) home town. Imagine that.

So I guess the moral of the story is that if you want to challenge somebody's credibility, you shouldn't use fudge to do it - it just ends up reflecting badly on you, at least among knowledgeable people. Then again, if you were concerned about your own credibility, you probably wouldn't be writing for boston.com!!