The manifest danger Islamic radicalism presents to the United States ought to be unifying American politicians around programs to keep the country safe. But their behavior this summer shows they prefer petty partisanship.

A series of decisions Congress must make in September – particularly on measures to authorize the National Security Agency’s Terrorist Surveillance Program and military tribunals for terrorist detainees – will determine whether they can find a common purpose.

The two sides should be looking at each others’ agendas – the Democrats’ advocacy of homeland security upgrades and some conservative ideas on terrorist “profiling”– to improve security.

And both should seriously consider the prospect of creating a domestic security agency like Great Britain’s MI5, particularly given the FBI’s evident failure – as reported in The Washington Post this week – to adapt its criminal investigation culture to antiterrorist intelligence-gathering.

But, based on the record, the prospects for cooperative action are not good. The minute Britain announced the arrest of radicals planning to blow up U.S.-bound airliners over the Atlantic, Republicans and Democrats began squabbling over what it meant – especially for their November election prospects.

Senate Minority Leader Harry Reid, D-Nev., put out a press release declaring the plot “demonstrates the need for the Bush administration and the Congress to change course in Iraq and ensure that we’re taking all the steps necessary to protect Americans at home and across the world.”