Senate Minority Leader Mitch McConnell's proposed Plan B for raising the debt ceiling — a classically congressional solution to a problem in that it accomplishes little but to shift accountability away from the legislative branch — is a terrible idea. It is terrible substantively, because it allows Washington to avoid any hard decisions about getting its fiscal situation under control, and it's terrible politically because it is a Trojan horse for President Barack Obama and a poison pill for tea party Republicans. The fact that it may soon seem like the best option is a testament to how close to the brink the nation has been driven by the culture of irrationality that has gripped a large swath of the Republican Party.

Mr. McConnell's idea calls for Congress to authorize President Obama to raise the debt in stages over the next two years, provided he specifies spending cuts to equal the amount of the increase (though he would not actually be required to carry them out). Congress could vote to override him on the debt limit increases, Mr. Obama could veto that, and, presumably, a sufficient number of representatives and senators would retain enough sanity to sustain the veto.

For many tea party types, this idea amounts to capitulation, as would anything that increases the debt ceiling. For Democrats, it sounds like suicide because it would make President Obama the one solely responsible for increasing the debt and would give Republicans multiple opportunities to vote against doing so without risking the actual consequences that would entail.

However, it represents the first genuinely new idea in what has otherwise grown into the political equivalent of trench warfare, and the stakes of allowing the stalemate to continue past Aug. 2, when the Treasury will run out of money to pay all the nation's bills, are becoming increasingly stark. Two major bond rating agencies signaled Wednesday that the United States is at risk of losing its AAA bond rating. One of them, Standard & Poor's, made clear that it could downgrade the nation even if it doesn't miss any of the interest payments on the debt but instead skips out on payments to retirees, veterans and others.

Those who say they are concerned about the level of federal debt should be particularly alarmed by that. A credit downgrade, by itself, would increase the deficit because the nation would pay higher interest rates on its debt. States and municipalities could also be affected, and the ripple effects on mortgages, car loans and other consumer credit would overwhelm the economy's fragile recovery.

Senator McConnell appealed to Republicans to support his idea by couching the consequences of default in political terms, saying it would guarantee Mr. Obama's re-election by saddling Republicans with the blame for the bad economy, much as the 1995 government shutdown benefited President Bill Clinton. That may be true, but it would also be terrible for the country. Once the AAA bond rating is lost, it may not be so easy to get back.

The key figure now is House Speaker John Boehner. Although he owes his job to the absolutists in the GOP's tea party wing, Mr. Boehner, like Senator McConnell, belongs to what might be called the Congressional Reality Caucus. Unlike many of the party's presidential candidates and a substantial number of his members in the House, Mr. Boehner is not in denial about the consequences of default, and he is keenly aware of what is possible in a divided government.

His earlier talks with President Obama about a deal to reduce the deficit by $4 trillion over the next decade through a mix of spending cuts and tax increases show his instinct is to accept compromise if it is in the best interests of the country. However, the fact that he walked away from that deal under pressure from House Majority Leader Eric Cantor, who has taken the lead in what might be called the Congressional Fantasy Caucus, shows the extent to which he is captive to the extremist wing of his party. Many newly elected Republicans say they are perfectly willing to lose the next election in order to maintain their ideological purity, but Mr. Boehner, evidently, is not yet willing to risk his position to do what he knows is right.

The speaker said Wednesday that no proposal that has yet been offered could get enough votes to pass the House of Representatives. That's surely not quite true. No deal may be able to get a majority in the House Republican Caucus, but that doesn't mean a proposal couldn't succeed with support from reasonable members of both parties. Mr. Boehner needs to remember that he is speaker of the House, not majority leader.

Meanwhile, President Obama should continue to push for as meaningful and permanent a solution to the twin problems of the debt limit and the long-term budget deficit as he can get. But if a plan like Mr. McConnell's is the only option to avoid default, he should take it. President Clinton may have cemented his re-election during the government shutdown, but the consequences of a default are far worse. If President Obama has to take the heat for an unpopular move that averts economic catastrophe, so be it. Nobody said being president was easy.