Mr. Obama is not just showing he’s a tax-and-spend liberal who will increase taxes to fund an ever larger welfare state. He is also abandoning a long-existing bipartisan consensus that encouraging savings and investment adds to prosperity. It was, after all, President John F. Kennedy who in 1963 said he cut capital gains taxes to affect “thereby the strength and potential growth of the economy.”

With the country’s serious economic challenges, all the president can offer is the Buffett Rule? Mr. Obama is shriveling before our eyes—not physically, but in stature and leadership. No wonder the average of all polls since Rick Santorum suspended his campaign April 11 shows Mr. Obama leading Mitt Romney by only 46.4% to 45.6%.

We may be at a political tipping point where acts confirm impressions that become impossible to shake. Mr. Obama is in danger of being seen as weak, inept and not up to the job. If Mr. Romney calls the president out on his small-minded political games and pivots to an ambitious reform agenda, he will make it much more likely that, come next January, Mr. Obama can turn his attention to writing his third autobiography.